Light emitting stacked structure and display device having the same

ABSTRACT

A light emitting stacked structure including a plurality of epitaxial sub-units disposed one over another, each epitaxial sub-unit configured to emit colored light having different wavelength band from each other, and a common electrode disposed between and connected to adjacent epitaxial sub-units, in which light emitting regions of the epitaxial sub-units overlap each other.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from and claims the benefit of U.S.Provisional Application No. 62/598,863, filed on Dec. 14, 2017, U.S.Provisional Application No. 62/598,823, filed on Dec. 14, 2017, and U.S.Provisional Application No. 62/617,038, filed on Jan. 12, 2018, each ofwhich is hereby incorporated by reference for all purposes as if fullyset forth herein.

BACKGROUND Field

Exemplary embodiments of the invention relate generally to a lightemitting stacked structure and a display device including the same and,more specifically, to a micro light emitting device having a stackedstructure and a display apparatus having the same.

Discussion of the Background

A light emitting diode has been widely used as an inorganic light sourcein various fields such as a display apparatus, an automobile lamp, andgeneral lighting. With advantages of long lifespan, low powerconsumption, and high response speed, the light emitting diode has beenrapidly replacing an existing light source.

Meanwhile, a light emitting diode of the related art has been mainlyused as a backlight light source in a display apparatus. However, amicro LED display has been recently developed as a next-generationdisplay that directly implements an image using a light emitting diode.

In general, the display apparatus implements various colors by usingmixed colors of blue, green, and red. The display apparatus includes aplurality of pixels to implement an image with various images, and eachpixel includes subpixels of has blue, green, and red. The color of aspecific pixel is determined by the colors of the subpixels, and theimage is implemented by the combination of these subpixels. In addition,a display device using LEDs may be generally manufactured by formingindividually grown red, green, and blue LED structures on a finalsubstrate, which may increase manufacturing complexity.

In the case of a micro LED display, micro LEDs corresponding to eachsubpixel are arranged on a two-dimensional plane. Therefore, a largenumber of micro LEDs are required to be disposed on one substrate.However, the micro LED has a very small size having a surface area of10,000 square μm or less, and thus, there are various problems due tothis small size. Particularly, it is difficult to handle a lightemitting diode having a small size, and it is not easy to mount thelight emitting diode on a display panel, especially over hundreds ofthousands or millions, and to replace a defective LED of mounted microLEDs with a good LED.

In addition, since the subpixels are arranged on the two-dimensionalplane, the area occupied by one pixel including the blue, green, and redsubpixels is relatively increased. Therefore, in order to arrange thesubpixels within a limited area, it is required to reduce the area ofeach subpixel, thereby causing deterioration in brightness throughreduction in luminous area.

The above information disclosed in this Background section is only forunderstanding of the background of the inventive concepts, and,therefore, it may contain information that does not constitute priorart.

SUMMARY

Light emitting stacked structures according to the principles and someexemplary implementations of the invention are capable of increasing alight emitting area of each subpixel without increasing the pixel area.

Light emitting diodes and display using the light emitting diodes, e.g.,micro LEDs, constructed according to the principles and some exemplaryimplementations of the invention provide an improved color purity andcolor reproduction.

Light emitting diodes and display using the light emitting diodes, e.g.,micro LEDs, constructed according to the principles and some exemplaryimplementations of the invention has a simple structure that can improveconnectivity between elements and/or reduce manufacturing complexities.

A light emitting stacked structure according to an exemplary embodimentincludes a plurality of epitaxial sub-units disposed one over another,each epitaxial sub-unit configured to emit light having differentwavelength bands from each other in a first direction, and a pluralityof contact parts disposed under the epitaxial sub-units to apply acommon voltage and light emitting signals to the epitaxial sub-units.

The light emitting stacked structure may further include a substratedisposed under the epitaxial sub-units and having wirings connected tothe contact parts.

The epitaxial sub-units may include a first epitaxial stack, a secondepitaxial stack, and a third epitaxial stack sequentially disposed onthe substrate.

The contact parts may include a common contact part to apply the commonvoltage to the first, second, and third epitaxial stacks, and a firstcontact part, a second contact part, and a third contact part may applythe light emitting signals to the first, second, and third epitaxialstacks, respectively.

Each of the first, second, and third epitaxial stacks may include ap-type semiconductor layer, an active layer, and an n-type semiconductorlayer, and the common contact part may be connected to the p-typesemiconductor layers of the first, second, and third epitaxial stacks,and the first, second, and third contact parts may be connected to then-type semiconductor layers of the first, second, and third epitaxialstacks, respectively.

The first epitaxial stack may have a recess exposing the n-typesemiconductor layer of the first epitaxial stack, and the first contactpart may be connected to the exposed n-type semiconductor layer of thefirst epitaxial stack in the recess.

The first contact part may include a first pad electrode disposed underthe first epitaxial stack, the first pad electrode may have a greaterwidth than the recess.

The first contact part may further include a first pad disposed underthe first pad electrode, the first pad having a greater width than therecess.

The second contact part and the third contact part may include a secondpad electrode and a third pad electrode disposed under the firstepitaxial stack, respectively.

The common contact part may include a common pad electrode disposedunder the first epitaxial stack.

The common pad electrode, the first, second, and third pad electrodesmay include substantially the same material and are disposed on the samelayer.

At least one of the n-type semiconductor layers of the second and thirdepitaxial stacks may have a concave-convex pattern formed on one surfacethereof.

The light emitting stacked structure may further include a first p-typeelectrode, a second p-type electrode, and a third p-type electrodeconnected to the p-type semiconductor layers of the first, second, andthird epitaxial stacks, respectively.

The first p-type electrode may be disposed between the substrate and thefirst epitaxial stack.

The second p-type electrode may be disposed between the first epitaxialstack and the second epitaxial stack, and the third p-type electrode maybe disposed between the second epitaxial stack and the third epitaxialstack.

At least one of the second p-type electrode and the third p-typeelectrode may include a transparent conductive material.

At least one of the second and third epitaxial stacks may have a firstcontact hole, and at least one of the second and third p-type electrodesmay have a second contact hole having a diameter different from thediameter of the first contact hole.

At least one of the epitaxial sub-units may include a micro LED having asurface area less than about 10,000 μm or less.

The epitaxial sub-units may include a first epitaxial sub-unit disposedon the substrate and configured to emit a first color light, a secondepitaxial sub-unit disposed on the first epitaxial sub-unit andconfigured to emit a second color light having a wavelength banddifferent from the first color light, and a third epitaxial sub-unitdisposed on the second epitaxial sub-unit and configured to emit a thirdcolor light having a wavelength band different from the first and secondcolor light.

The first color light, the second color light, and the third color lightmay be red light, green light, and blue light, respectively.

The light emitting stacked structure may further include a firstwavelength pass filter disposed between the first epitaxial sub-unit andthe second epitaxial sub-unit.

The light emitting stacked structure may further include a secondwavelength pass filter disposed between the second epitaxial sub-unitand the third epitaxial sub-unit.

The wirings may include a first signal line, a second signal line, and athird signal line to apply the light emitting signals to n-typesemiconductor layers of the first, second, and third epitaxialsub-units, respectively.

The light emitted from the epitaxial sub-units may have energy bandsdifferent from each other, and the energy bands of the light mayincrease along the first direction.

The epitaxial sub-units may be independently drivable.

Light emitted from a lower epitaxial sub-unit may be configured to betransmitted through an upper epitaxial sub-unit.

Each of the epitaxial sub-unit may be configured to transmit at leastabout 80% of light emitted from a lower epitaxial stack.

A display device may include a plurality of pixels, at least one ofpixels may include the light emitting stacked structure according to anexemplary embodiment.

The display device may be configured to be driven in a passive matrixmanner.

The display device may be configured to be driven in an active matrixmanner.

A light emitting stacked structure according to an exemplary embodimentincludes a plurality of epitaxial sub-units disposed one over another,each epitaxial sub-unit configured to emit colored light havingdifferent wavelength band from each other, and a common electrodedisposed between and connected to adjacent epitaxial sub-units, in whichlight emitting regions of the epitaxial sub-units overlap each other.

The epitaxial sub-units may include a first epitaxial stack, a secondepitaxial stack, and a third epitaxial stack sequentially disposed oneover another.

The common electrode may include a shared electrode disposed between oneof i) the first epitaxial stack and the second epitaxial stack, and ii)the second epitaxial stack and the third epitaxial stack.

The light emitting stacked structure may further include a contact partdisposed on the epitaxial sub-units to apply a common voltage and lightemitting signals, the contact part may include a common contact part toapply the common voltage to the first, second, and third epitaxialstacks, and a first contact part, a second contact part, and a thirdcontact part to apply the light emitting signals to the first, second,and third epitaxial stacks, respectively.

The light emitting stacked structure may further include a first signalline, a second signal line, and a third signal line to apply the lightemitting signals to the first, second, and third epitaxial stacks,respectively, and a common line applying the common voltage to thefirst, second, and third epitaxial stacks, and the first, second, andthird signal lines may be connected to the first, second, and thirdcontact parts, respectively, and the common line may be connected to thecommon contact part.

The first, second, and third signal lines may extend in a firstdirection and the common line may extend in a second directionintersecting the first direction.

The common contact part may include a first common contact electrode, asecond common contact electrode, and a third common contact electrode toapply the common voltage to the first, second, and third epitaxialstacks, respectively, and the second and third common contact electrodesmay include the shared electrode.

Each of the first, second, and third epitaxial stacks may include ap-type semiconductor layer, an active layer, and an n-type semiconductorlayer.

A stacked sequence of the n-type semiconductor layer, the active layer,and the p-type semiconductor layer in the second epitaxial stack may bedifferent from that in at least one of the first and third epitaxialstacks.

The shared electrode may directly contact the p-type semiconductor layerof the second epitaxial stack and the p-type semiconductor layer of thethird epitaxial stack.

In the second epitaxial stack, the p-type semiconductor layer, theactive layer, and the n-type semiconductor layer may be stackedsequentially, and in the third epitaxial stack, the n-type semiconductorlayer, the active layer, and the p-type semiconductor layer may bestacked sequentially.

The shared electrode may directly contact the n-type semiconductor layerof the second epitaxial stack and the n-type semiconductor layer of thethird epitaxial stack.

The light emitting stacked structure may further include a wavelengthpass filter disposed between the second common contact electrode and thethird common contact electrode.

The second and third common contact electrodes may be connected to eachother through a contact hole provided in the wavelength pass filter.

The first common contact electrode may be disposed under the firstepitaxial stack.

The light emitting stacked structure may further include an insulatinglayer covering the first, second, and third epitaxial stacks, in whichthe first common contact electrode may be connected to the second andthird common contact electrodes through a contact hole formed in theinsulating layer.

Energy bands of light emitted from the epitaxial sub-units may increasefrom a lowermost epitaxial sub-unit to an uppermost epitaxial sub-unit.

The epitaxial sub-units may be independently drivable.

Light emitted from a lower epitaxial sub-unit may be configured totransmit through an upper epitaxial sub-unit.

Each of the epitaxial sub-units may be configured to transmit at leastabout 80% of light emitted from a lower epitaxial sub-unit.

The epitaxial sub-units may include a first epitaxial stack disposed ona substrate and configured to emit a first color light, a secondepitaxial stack disposed on the first epitaxial stack and configured toemit a second color light having a wavelength band different from thefirst color light, and a third epitaxial stack disposed on the secondepitaxial stack and configured to emit a third color light having awavelength band different from the first and second color light.

The first color light, the second color light, and the third color lightmay be red light, green light, and blue light, respectively.

The light emitting stacked structure may further include a firstwavelength pass filter disposed between the first epitaxial stack andthe second epitaxial stack.

The light emitting stacked structure may further include a secondwavelength pass filter disposed between the second epitaxial stack andthe third epitaxial stack.

At least one of the first to third epitaxial stacks may have aconcave-convex pattern formed on one upper surface thereof

A display device may include a plurality of pixels, at least one whichmay be comprised the light emitting stacked structure according to anexemplary embodiment.

The display device may be driven in a passive matrix manner.

The display device may be driven in an active matrix manner.

A display apparatus according to an exemplary embodiment includes a thinfilm transistor (TFT) substrate, electrode pads disposed on an uppersurface of the TFT substrate, a first light emitting diode (LED)sub-unit disposed on the TFT substrate, a second LED sub-unit disposedon the first LED sub-unit, a third LED sub-unit disposed on the secondLED sub-unit, connectors electrically connecting the first, second, andthird LED sub-units to the electrode pads, and a first layer disposedbetween the first LED sub-unit and the TFT substrate, the first layerbeing electrically connected to n-type semiconductor layers of thefirst, second, and third LED sub-units, in which the first, second, andthird LED sub-units are independently drivable, light generated in thefirst LED sub-unit is configured to be emitted to the outside of thedisplay device through the second and third LED sub-units, and lightgenerated in the second LED sub-unit is configured to be emitted to theoutside of the display device through the third LED sub-unit.

The first, second, and third LED sub-units may include first, second,and third LED stacks configured to emit red light, green light, and bluelight, respectively.

The display apparatus may further include pads disposed between thefirst LED sub-unit and the TFT substrate and bonded to the electrodepads, in which p-type semiconductor layers of the first, second, andthird LED sub-units may be electrically connected to different pads,respectively.

At least one of the pads may be electrically connected to the firstlayer.

The display apparatus may further include second auxiliary electrodeseach disposed between the pads and the first LED sub-unit, the secondauxiliary electrodes and the first layer may include substantially thesame material.

The first layer may include a ground layer continuously disposed over aplurality of pixel regions.

The display apparatus may further include a first reflective electrodein ohmic contact with the p-type semiconductor layer of the first LEDsub-unit, in which the first reflective electrode may be insulated fromthe first layer, and a portion of the first reflective electrode isinterposed between the first layer and the TFT substrate.

The first reflective electrode may include an ohmic contact layer and areflective layer.

The display apparatus may further include first auxiliary electrodesdisposed on the same layer and comprising the same material as thereflective layer.

The connectors may include a first lower connector, a second lowerconnector, and a third lower connector passing through the first LEDsub-unit, the first lower connector may be electrically connected to then-type semiconductor layer of the first LED sub-unit, and the secondlower connector and the third lower connector may be electricallyinsulated from the first LED sub-unit and are electrically connected tothe electrode pads, respectively.

The connectors may further include a first middle connector, a secondmiddle connector, and a third middle connector passing through thesecond LED sub-unit, the first middle connector may electrically connectthe n-type semiconductor layer of the second LED sub-unit to the firstlower connector, the second middle connector may electrically connect ap-type semiconductor layer of the second LED sub-unit to the secondlower, and the third middle connector may be electrically insulated fromthe second LED sub-unit and be connected to the third lower connector.

The display apparatus may further include a second transparent electrodeinterposed between the first LED sub-unit and the second LED sub-unitand in ohmic contact with the p-type semiconductor layer of the secondLED sub-unit, in which the second lower connector may be connected tothe second transparent electrode.

The connectors may further include a first upper connector and a secondupper connector passing through the third LED sub-unit, the first upperconnector may electrically connect the n-type semiconductor layer of thethird LED sub-unit to the first middle connector, and the second upperconnector may electrically connect a p-type semiconductor layer of thethird LED sub-unit to the third middle connector.

The display apparatus may further include a third transparent electrodeinterposed between the second LED sub-unit and the third LED sub-unitand in ohmic contact with the p-type semiconductor layer of the thirdLED sub-unit, in which the second upper connector may be connected tothe third transparent electrode.

The first lower connector, the first middle connector, and the firstupper connector may be stacked in a substantially vertical direction,the second lower connector and the second middle connector may bestacked in a substantially vertical direction, and the third lowerconnector, the third middle connector, and the second upper connectormay be stacked in a substantially vertical direction.

The display apparatus may further include a first color filterinterposed between the first LED sub-unit and the second LED sub-unit totransmit light generated in the first LED sub-unit, and reflect lightgenerated in the second LED sub-unit, and a second color filterinterposed between the second LED sub-unit and the third LED sub-unit totransmit light generated in the first and second LED sub-units, andreflect light generated in the third LED sub-unit.

The display apparatus may further include an underfill interposedbetween the TFT substrate and the first LED sub-unit.

The display apparatus may further include a first bonding layerinterposed between the first LED sub-unit and the second LED sub-unit,and a second bonding layer interposed between the second LED sub-unitand the third LED sub-unit, in which the first bonding layer may beconfigured to transmit light generated in the first LED sub-unit, andthe second bonding layer may be configured to transmit light generatedin the first LED sub-unit and the second LED sub-unit.

The display apparatus may further include a light guide disposed abovethe third LED sub-unit.

The display apparatus may further include a micro lens disposed on thelight guide.

The display apparatus may further include a plurality of unit pixelsdisposed on the TFT substrate, in which at least one of the unit pixelsmay include the electrode pads, the first LED sub-unit, the second LEDsub-unit, the third LED sub-unit, the connectors, and the first layer.

At least one of the unit pixels may include a micro LED having a surfacearea less than about 10,000 μm

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate exemplary embodiments of theinvention, and together with the description serve to explain theinventive concepts.

FIG. 1 is a schematic cross-sectional view of a light emitting stackedstructure according to an exemplary embodiment.

FIGS. 2A and 2B are cross-sectional views of a light emitting stackedstructure according to exemplary embodiments.

FIG. 3 is a cross-sectional view of a light emitting stacked structureaccording to an exemplary embodiment.

FIGS. 4, 5, and 6 are cross-sectional view of a light emitting stackedstructure according to exemplary embodiments.

FIG. 7 is a plan view of a display device according to an exemplaryembodiment.

FIG. 8 is an enlarged plan view of portion P1 of FIG. 7.

FIG. 9 is a block diagram illustrating a display device according to anexemplary embodiment.

FIG. 10 is a circuit diagram illustrating one subpixel in a passive-typedisplay device according to an exemplary embodiment.

FIG. 11 is a circuit diagram illustrating one subpixel in an active-typedisplay device according to an exemplary embodiment.

FIG. 12 is a plan view of a pixel according to an exemplary embodiment.

FIG. 13 is a cross-sectional view taken along line I-I′ of FIG. 12.

FIGS. 14, 16, 18, 20, 22, 24, 26, 28, 30, and 32 are plan viewsillustrating a method of forming first, second, and third epitaxialstacks on a substrate according to an exemplary embodiment.

FIGS. 15A, 15B, 17, 19A, 19B, 21, 23, 25A, 25B, 27A, 27B, 29, 31A, 31B,31C, 31D, 31E, 33A, 33B, 33C, 33D, and 33E are cross-sectional viewstaken along line I-I′ of corresponding plan view according to anexemplary embodiment.

FIGS. 34A to 34D are enlarged sectional views illustrating a portioncorresponding to P2 of FIG. 27A.

FIG. 35 is a schematic cross-sectional view of a light emitting stackedstructure according to an exemplary embodiment.

FIGS. 36A and 36B are cross-sectional views a light emitting stackedstructure according to exemplary embodiments.

FIG. 37 is a schematic cross-sectional view of a light emitting stackedstructure according to an exemplary embodiment.

FIGS. 38 and 39 are schematic cross-sectional views of a light emittingstacked structure according to exemplary embodiments.

FIG. 40 is a plan view of a display device according to an exemplaryembodiment.

FIG. 41 is an expanded perspective view of portion P1 of FIG. 40.

FIG. 42 is a block diagram of a display device according to an exemplaryembodiment.

FIG. 43 is a circuit diagram of a subpixel in a passive-type displaydevice according to an exemplary embodiment.

FIG. 44 is a circuit diagram of a subpixel in an active-type displaydevice according to an exemplary embodiment.

FIG. 45 is a plan view of a pixel according to an exemplary embodiment.

FIG. 46 is a cross-sectional view taken along line I-I′ of FIG. 45.

FIGS. 47, 49, 51, 53, 55, and 57 are plan views illustrating a method ofsequentially stacking first, second, and third epitaxial stacks on asubstrate according to an exemplary embodiment.

FIGS. 48, 50A, 50B, and 50C, 52A, 52B, 52C, 52D, 52E, 52F, 52G, and 52H,54A, 54B, 54C, and 54D, 56, and 58 are cross-sectional views taken alongline I-I′ of FIGS. 47, 49, 51, 53, 55, and 57.

FIG. 59A is a schematic plan view of a display apparatus according to anexemplary embodiment.

FIG. 59B is a schematic cross-sectional view taken along line A-B ofFIG. 59A.

FIG. 60 is a schematic circuit diagram of a display apparatus accordingto an exemplary embodiment.

FIGS. 61A, 61B, 62A, 62B, 63A, 63B, 64A, 64B, 65A, 65B, 66A, 66B, 67A,67B, 68A, 68B, 69A, 69B, 70A, 70B, 71A, 71B, 72A, 72B, 73A, 73B, 74A,74B, 75A, and 75B are schematic plan views and cross-sectional viewsillustrating a method of manufacturing a display apparatus according toan exemplary embodiment.

FIGS. 76A and 76B are a schematic plan view and cross-sectional view ofa display apparatus according to another exemplary embodiment,respectively.

FIGS. 77A and 77B are a schematic plan view and cross-sectional viewillustrating a display apparatus according to another exemplaryembodiment, respectively.

FIG. 78 is a schematic cross-sectional view of a display apparatusaccording to still another exemplary embodiment.

FIG. 79 is a schematic cross-sectional view illustrating a displayapparatus according to yet still another exemplary embodiment.

FIGS. 80A, 80B, 80C, and 80D are schematic cross-sectional views adisplay apparatus according to exemplary embodiments.

FIG. 81 is a schematic cross-sectional view of a display apparatusaccording to yet still another exemplary embodiment.

DETAILED DESCRIPTION

In the following description, for the purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of various exemplary embodiments or implementations of theinvention. As used herein “embodiments” and “implementations” areinterchangeable words that are non-limiting examples of devices ormethods employing one or more of the inventive concepts disclosedherein. It is apparent, however, that various exemplary embodiments maybe practiced without these specific details or with one or moreequivalent arrangements. In other instances, well-known structures anddevices are shown in block diagram form in order to avoid unnecessarilyobscuring various exemplary embodiments. Further, various exemplaryembodiments may be different, but do not have to be exclusive. Forexample, specific shapes, configurations, and characteristics of anexemplary embodiment may be used or implemented in another exemplaryembodiment without departing from the inventive concepts.

Unless otherwise specified, the illustrated exemplary embodiments are tobe understood as providing exemplary features of varying detail of someways in which the inventive concepts may be implemented in practice.Therefore, unless otherwise specified, the features, components,modules, layers, films, panels, regions, and/or aspects, etc.(hereinafter individually or collectively referred to as “elements”), ofthe various embodiments may be otherwise combined, separated,interchanged, and/or rearranged without departing from the inventiveconcepts.

The use of cross-hatching and/or shading in the accompanying drawings isgenerally provided to clarify boundaries between adjacent elements. Assuch, neither the presence nor the absence of cross-hatching or shadingconveys or indicates any preference or requirement for particularmaterials, material properties, dimensions, proportions, commonalitiesbetween illustrated elements, and/or any other characteristic,attribute, property, etc., of the elements, unless specified. Further,in the accompanying drawings, the size and relative sizes of elementsmay be exaggerated for clarity and/or descriptive purposes. When anexemplary embodiment may be implemented differently, a specific processorder may be performed differently from the described order. Forexample, two consecutively described processes may be performedsubstantially at the same time or performed in an order opposite to thedescribed order. Also, like reference numerals denote like elements.

When an element, such as a layer, is referred to as being “on,”“connected to,” or “coupled to” another element or layer, it may bedirectly on, connected to, or coupled to the other element or layer orintervening elements or layers may be present. When, however, an elementor layer is referred to as being “directly on,” “directly connected to,”or “directly coupled to” another element or layer, there are nointervening elements or layers present. To this end, the term“connected” may refer to physical, electrical, and/or fluid connection,with or without intervening elements. Further, the D1-axis, the D2-axis,and the D3-axis are not limited to three axes of a rectangularcoordinate system, such as the x, y, and z-axes, and may be interpretedin a broader sense. For example, the D1-axis, the D2-axis, and theD3-axis may be perpendicular to one another, or may represent differentdirections that are not perpendicular to one another. For the purposesof this disclosure, “at least one of X, Y, and Z” and “at least oneselected from the group consisting of X, Y, and Z” may be construed as Xonly, Y only, Z only, or any combination of two or more of X, Y, and Z,such as, for instance, XYZ, XYY, YZ, and ZZ. As used herein, the term“and/or” includes any and all combinations of one or more of theassociated listed items.

Although the terms “first,” “second,” etc. may be used herein todescribe various types of elements, these elements should not be limitedby these terms. These terms are used to distinguish one element fromanother element. Thus, a first element discussed below could be termed asecond element without departing from the teachings of the disclosure.

Spatially relative terms, such as “beneath,” “below,” “under,” “lower,”“above,” “upper,” “over,” “higher,” “side” (e.g., as in “sidewall”), andthe like, may be used herein for descriptive purposes, and, thereby, todescribe one elements relationship to another element(s) as illustratedin the drawings. Spatially relative terms are intended to encompassdifferent orientations of an apparatus in use, operation, and/ormanufacture in addition to the orientation depicted in the drawings. Forexample, if the apparatus in the drawings is turned over, elementsdescribed as “below” or “beneath” other elements or features would thenbe oriented “above” the other elements or features. Thus, the exemplaryterm “below” can encompass both an orientation of above and below.Furthermore, the apparatus may be otherwise oriented (e.g., rotated 90degrees or at other orientations), and, as such, the spatially relativedescriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particularembodiments and is not intended to be limiting. As used herein, thesingular forms, “a,” “an,” and “the” are intended to include the pluralforms as well, unless the context clearly indicates otherwise. Moreover,the terms “comprises,” “comprising,” “includes,” and/or “including,”when used in this specification, specify the presence of statedfeatures, integers, steps, operations, elements, components, and/orgroups thereof, but do not preclude the presence or addition of one ormore other features, integers, steps, operations, elements, components,and/or groups thereof. It is also noted that, as used herein, the terms“substantially,” “about,” and other similar terms, are used as terms ofapproximation and not as terms of degree, and, as such, are utilized toaccount for inherent deviations in measured, calculated, and/or providedvalues that would be recognized by one of ordinary skill in the art.

Various exemplary embodiments are described herein with reference tosectional and/or exploded illustrations that are schematic illustrationsof idealized exemplary embodiments and/or intermediate structures. Assuch, variations from the shapes of the illustrations as a result, forexample, of manufacturing techniques and/or tolerances, are to beexpected. Thus, exemplary embodiments disclosed herein should notnecessarily be construed as limited to the particular illustrated shapesof regions, but are to include deviations in shapes that result from,for instance, manufacturing. In this manner, regions illustrated in thedrawings may be schematic in nature and the shapes of these regions maynot reflect actual shapes of regions of a device and, as such, are notnecessarily intended to be limiting.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure is a part. Terms,such as those defined in commonly used dictionaries, should beinterpreted as having a meaning that is consistent with their meaning inthe context of the relevant art and should not be interpreted in anidealized or overly formal sense, unless expressly so defined herein.

As used herein, a light emitting stacked structure or a light emittingdiode according to exemplary embodiments may include a micro LED, whichhas a surface area less than about 10,000 square μm as known in the art.In other exemplary embodiments, the micro LED's may have a surface areaof less than about 4,000 square μm, or less than about 2,500 square μm,depending upon the particular application. In addition, a light emittingdevice may be mounted in various configurations, such as flip bonding,and thus, the inventive concepts are not limited to a particular stackedsequence of the first, second, and third LED stacks.

FIG. 1 is a schematic cross-sectional view of a light emitting stackedstructure according to an exemplary embodiment.

Referring to FIG. 1, a light emitting stacked structure according to anexemplary embodiment includes a plurality of epitaxial stacks, which aresequentially stacked on a substrate 10. The substrate 10 is provided inthe form of a plate having a front surface and a back surface.

The epitaxial stacks may be mounted on the front surface of thesubstrate 10, and the substrate 10 may be provided in various forms. Forexample, the substrate 10 may be formed of an insulating material. Thematerial of the substrate 10 may include glass, quartz, organic polymer,organic/inorganic composite, etc. However, the inventive concepts arenot limited to a particular material forming the substrate 10, and thesubstrate 10 may include various materials as long as it has aninsulating property. In an exemplary embodiment, a wire part providing alight emitting signal and a common voltage to each epitaxial stack maybe disposed on the substrate 10. In particular, when each epitaxialstack is driven in an active matrix manner, a driving element includinga thin film transistor may be further disposed on the substrate 10 inaddition to the wire part. In this case, the substrate 10 may be formedas a printed circuit substrate, or as a complex substrate, in which thewire part and/or the driving element are formed on the glass, silicon,quartz, organic polymer, or organic/inorganic composite.

The epitaxial stacks may be sequentially stacked on the front surface ofthe substrate 10. Each of the plurality of epitaxial stacks emits alight.

In an exemplary embodiment, the number of epitaxial stacks may be two ormore, and the epitaxial stacks may emit light in different wavelengthbands, respectively. In particular, the epitaxial stacks may havedifferent energy bands. Hereinafter, the light emitting stackedstructure will be described as including three epitaxial stack layers20, 30, and 40 sequentially stacked on the substrate 10, however, theinventive concepts are not limited to a particular number of epitaxialstacked layers.

Each epitaxial stack may emit a color light in a visible light bandamong various wavelength bands. In an exemplary embodiment, lightemitted from an epitaxial stack disposed on the lowermost may be a colorlight having the longest wavelength, which has the lowest energy band.Epitaxial stacks disposed thereon may sequentially emit color lighthaving a shorter wavelength from the lowermost toward the uppermost. Inthis manner, light emitted from an epitaxial stack disposed on theuppermost may be a color light of the shortest wavelength, which has thehighest energy band. For example, the first epitaxial stack 20 may emita first color light L1, a second epitaxial stack 30 may emit a secondcolor light L2, and a third epitaxial stack 40 may emit a third colorlight L3. Here, the first to third color lights L1 to L3 may correspondto different color lights, the first to third color lights L1 to L3 maybe color light in different wavelength bands, and the wavelengths of thefirst to third color lights L1 to L3 may become sequentially short. Inparticular, the first to third color lights L1 to L3 may have differentwavelength bands, and color light may have a shorter wavelength band,the energy of which become higher, as it goes from the first color lightL1 toward the third color light L3.

In the illustrated exemplary embodiment, the first color light L1 may bea red light, the second color light L2 may be a green light, and thethird color light L3 may be a blue light. However, the inventiveconcepts are not limited thereto. When the light emitting stackedstructure includes a micro LED, which has a surface area less than about10,000 square μm as known in the art, or less than about 4,000 square μmor 2,500 square μm in other exemplary embodiments, the first epitaxialstack 20 may emit any one of red, green, and blue light, and the secondand third epitaxial stacks 30 and 40 may emit a different one of red,green, and blue light, without adversely affecting operation, due to thesmall form factor of a micro LED.

Each of the epitaxial stacks 20, 30, and 40 emits a light in thedirection (hereinafter referred to as a “front direction”) of the frontsurface of the substrate 10. For example, light emitted from oneepitaxial stack travels in the front direction through any otherepitaxial stack(s) located in a path of light. Here, the “frontdirection” may refer to a direction in which the first, second, andthird epitaxial stacks 20, 30, and 40 are stacked from the substrate 10.

Hereinafter, the “front direction” of the substrate 10 may refer to an“upper direction” and the “back direction” of the substrate 10 may referto a “lower direction.” However, the terms above defined, that is, the“upper direction” and the “lower direction” are relative directions, andmay vary with a direction in which epitaxial stacks of the lightemitting stacked structure is arranged or stacked.

Each of the epitaxial stacks 20, 30, and 40 emits light in the upperdirection, and each of the epitaxial stacks 20, 30, and 40 transmitsmost of light emitted from a epitaxial stack disposed thereunder. Inparticular, light emitted from the first epitaxial stack 20 passesthrough the second epitaxial stack 30 and the third epitaxial stack 40to travel in the front direction, and light emitted from the secondepitaxial stack 30 passes through the third epitaxial stack 40 to travelin the front direction. As such, at least some or all of the remainingepitaxial stacks other than the lowermost epitaxial stack may be formedof a light-transmitting material. The light-transmitting material may bea material transmitting light of a particular wavelength or a portion oflight of the particular wavelength, or a material transmitting wholelight. In an exemplary embodiment, each of the epitaxial stacks 20, 30,and 40 may transmit 60% or more of light emitted from an epitaxial stackdisposed thereunder. In another exemplary embodiment, each of theepitaxial stacks 20, 30, and 40 may transmit 80% or more of lightemitted from an epitaxial stack disposed thereunder. In anotherexemplary embodiment, each of the epitaxial stacks 20, 30, and 40 maytransmit 90% or more of light emitted from an epitaxial stack disposedthereunder.

The epitaxial stacks 20, 30, and 40 of the light emitting stackedstructure according to an exemplary embodiment may be independentlydriven by connecting signal lines that apply light emitting signals tothe epitaxial stacks, respectively. Also, the light emitting stackedstructure according to an exemplary embodiment may implement variouscolors depending on whether light is emitted from the epitaxial stacks20, 30, and 40. Also, since epitaxial stacks emitting light of differentwavelengths are formed to vertically overlap each other, it is possibleto form the light emitting stacked structure.

FIGS. 2A and 2B are cross-sectional views of a light emitting stackedstructure according to exemplary embodiments.

Referring to FIG. 2A, the light emitting stacked structure according toan exemplary embodiment includes the first, second, and third epitaxialstacks 20, 30, and 40 disposed on the substrate 10 with first, second,and third adhesive layers 60 a, 60 b, and 60 c interposed therebetween.The first adhesive layer 60 a may be formed of a conductive ornon-conductive material. In some exemplary embodiments, a portion of thefirst adhesive layer 60 a may have conductivity to electrically connectthe first adhesive layer 60 a to the substrate 10. The first adhesivelayer 60 a may be formed of a transparent or opaque material. In anexemplary embodiment, when the substrate 10 is formed of an opaquematerial and a wire part and the like are formed on the substrate 10,the first adhesive layer 60 a may be formed of an opaque material, forexample, a material that absorbs light. Various polymer adhesives, forexample, an epoxy-based polymer adhesive may be used as a lightabsorption material for the first adhesive layer 60 a.

The second and third adhesive layers 60 b and 60 c are formed of anon-conductive material and may include a light-transmitting material.For example, an optically clear adhesive may be used as the second andthird adhesive layers 60 b and 60 c. The second and third adhesivelayers 60 b and 60 c may include various materials as long as they areoptically clear and can be stably adhered to each epitaxial stack. Forexample, the second and third adhesive layers 60 b and 60 c may includeepoxy polymer, various photoresists, parylene, PMMA (Poly(methylmethacrylate)), BCB (benzocyclobutene), etc., such as SU-8, as anorganic material, and may include silicon oxide, aluminum oxide, moltenglass, etc., as an inorganic material. In some exemplary embodiments,conductive oxide may be used as an adhesive layer. In this case, theconductive oxide should be insulated from any other element. When anorganic material or molten glass of the inorganic materials is used asan adhesive layer, the material may be coated on an adhesive surface andmay be bonded thereon at a high temperature and a high pressure in avacuum state. When an inorganic material (except for molten glass) isused as an adhesive layer, the inorganic material may be bonded on anadhesive layer through deposition of the inorganic material on theadhesive layer, chemical-mechanical planarization (CMP), plasmaprocessing on a surface of a resultant structure, and bonding at highvacuum, for example.

The first epitaxial stack 20 includes a p-type semiconductor layer 25,an active layer 23, and an n-type semiconductor layer 21 sequentiallystacked one over one another. The second epitaxial stack 30 includes ap-type semiconductor layer 35, an active layer 33, and an n-typesemiconductor layer 31 sequentially stacked one over one another. Thethird epitaxial stack 40 include a p-type semiconductor layer 45, anactive layer 43, and an n-type semiconductor layer 41 sequentiallystacked one over one another.

The p-type semiconductor layer 25, the active layer 23, and the n-typesemiconductor layer 21 of the first epitaxial stack 20 may include asemiconductor material emitting a red light, for example.

The semiconductor material emitting a red light may include aluminumgallium arsenide (AlGaAs), gallium arsenide phosphide (GaAsP), aluminumgallium indium phosphide (AlGaInP), gallium phosphide (GaP), etc.,without being limited thereto.

A first p-type contact electrode 27 may be provided under the p-typesemiconductor layer 25 of the first epitaxial stack 20. The first p-typecontact electrode 27 of the first epitaxial stack 20 may be formed of asingle-layered or multi-layered metal. For example, various materialsincluding metals, such as Al, Ti, Cr, Ni, Au, Ag, Ti, Sn, Ni, Cr, W, andCu, or an alloy thereof may be used as the first p-type contactelectrode 27. The first p-type contact electrode 27 may include a metalhave high reflectivity to improve light output efficiency of the firstepitaxial stack 20 in the upper direction.

The second epitaxial stack 30 includes the p-type semiconductor layer35, the active layer 33, and the n-type semiconductor layer 31sequentially stacked. The p-type semiconductor layer 35, the activelayer 33, and the n-type semiconductor layer 31 may include asemiconductor material emitting a green light, for example. Thesemiconductor material emitting a green light may include indium galliumnitride (InGaN), gallium nitride (GaN), allium phosphide (GaP), AlGaInP,AlGaP, etc., without being limited thereto.

A second p-type contact electrode 37 is provided under the p-typesemiconductor layer 35 of the second epitaxial stack 30. The secondp-type contact electrode 37 is interposed between the first epitaxialstack 20 and the second epitaxial stack 30, in detail, between thesecond adhesive layer 60 b and the second epitaxial stack 30.

The third epitaxial stack 40 includes the p-type semiconductor layer 45,the active layer 43, and the n-type semiconductor layer 41 sequentiallystacked. The p-type semiconductor layer 45, the active layer 43, and then-type semiconductor layer 41 may include a semiconductor materialemitting a blue light, for example. The semiconductor material emittinga blue light may include GaN, InGaN, zinc selenide (ZnSe), etc., withoutbeing limited thereto.

A third p-type contact electrode 47 is provided under the p-typesemiconductor layer 45 of the third epitaxial stack 40. The third p-typecontact electrode 47 is interposed between the second epitaxial stack 30and the third epitaxial stack 40, in detail, between the third adhesivelayer 60 c and the third epitaxial stack 40.

In the illustrated exemplary embodiment, each of the n-typesemiconductor layers 21, 31, and 41 and the p-type semiconductor layers25, 35, and 45 of the first, second, and third epitaxial stacks 20, 30,and 40 is illustrated as having a single layer structure, but in someexemplary embodiments, each layer may have a multi-layer structure ormay include a supperlattic layer. Also, the active layers 23, 33, and 43of the first, second, and third epitaxial stacks 20, 30, and 40 mayinclude a single quantum well structure or a multiple quantum wellstructure.

The second and third p-type contact electrodes 37 and 47 substantiallycover the second and third epitaxial stacks 30 and 40. The second andthird p-type contact electrodes 37 and 47 may be formed of a transparentconductive material, which may transmit light emitted from an epitaxialstack disposed thereunder. For example, each of the second and thirdp-type contact electrodes 37 and 47 may be formed of transparentconductive oxide (TCO). The transparent conductive oxide may include tinoxide (SnO), indium oxide (InO₂), zinc oxide (ZnO), indium tin oxide(ITO), indium tin zinc oxide (ITZO). etc. A transparent conductivecompound may be deposited through chemical vapor deposition (CVD) andphysical vapor deposition (PVD) by using an evaporator and a sputter.The second and third p-type contact electrodes 37 and 47 may have athickness enough to function as an etch stopper in a fabricatingprocess, which will be described in more detail later, within the limitssatisfying transmittance, for example, a thickness of approximately 2000angstroms or approximately 2 micrometers.

A common line may be connected to the first, second, and third p-typecontact electrodes 27, 37, and 47. The common line may be a linesupplying a common voltage. Also, light emitting signal lines may berespectively connected to the n-type semiconductor layers 21, 31, and 41of the first, second, and third epitaxial stacks 20, 30, and 40. In anexemplary embodiment, a common voltage S_(c) is applied to the firstp-type contact electrode 27, the second p-type contact electrode 37, andthe third p-type contact electrode 47 through the common line, and thelight emission of the first, second, and third epitaxial stacks 20, 30,and 40 are controlled by applying light emitting signals to the n-typesemiconductor layers 21, 31, and 41 of the first, second, and thirdepitaxial stacks 20, 30, and 40 through the light emitting signal lines,respectively. The light emitting signals may include first, second, andthird light emitting signals S_(R), S_(G), and S_(B) respectivelycorresponding to the first, second, and third epitaxial stacks 20, 30,and 40. In an exemplary embodiment, the first light emitting signalS_(R) may be a signal for emitting a red light, the second lightemitting signal S_(G) may be a signal for emitting a green light, andthe third light emitting signal S_(B) may be a signal for emitting ablue light.

Although the common voltage is described as being applied to the p-typesemiconductor layers 25, 35, and 45 of the first, second, and thirdepitaxial stacks 20, 30, and 40 and the light emitting signals S_(R),S_(G), and S_(B) are described as being respectively applied to then-type semiconductor layers 21, 31, and 41 of the first, second, andthird epitaxial stacks 20, 30, and 40, the inventive concepts are notlimited thereto. In another exemplary embodiment, the common voltage maybe applied to the n-type semiconductor layers 21, 31, and 41 of thefirst, second, and third epitaxial stacks 20, 30, and 40, and the lightemitting signals S_(R), S_(G), and S_(B) may be applied to the p-typesemiconductor layers 25, 35, and 45 of the first, second, and thirdepitaxial stacks 20, 30, and 40, respectively.

FIG. 2B is a cross-sectional view of a light emitting stacked structureaccording to an exemplary embodiment of the inventive concept, in whichthe common voltage is applied to the n-type semiconductor layers 21, 31,and 41 of the first, second, and third epitaxial stacks 20, 30, and 40,and the light emitting signals S_(R), S_(G), and S_(B) are respectivelyapplied to the p-type semiconductor layers 25, 35, and 45 of the first,second, and third epitaxial stacks 20, 30, and 40.

Referring to FIG. 2B, light emitting stacked structure according to theillustrated exemplary embodiment is substantially similar to that ofFIG. 2A, except that layers of the epitaxial stacks 20, 30, and 40 areformed in the order of the n-type semiconductor layers 21, 31, and 41,the active layers 23, 33, and 43, and the p-type semiconductor layers25, 35, and 45. In this case, n-type contact electrodes 29, 39, and 49may be provided under the n-type semiconductor layers 21, 31, and 41,respectively. As such, detailed descriptions of the substantiallysimilar elements will be omitted to avoid redundancy.

According to the exemplary embodiments, the first, second, and thirdepitaxial stacks 20, 30, and 40 are driven in response to relevant lightemitting signals, respectively. More particularly, the first epitaxialstack 20 is driven by the first light emitting signal S_(R), the secondepitaxial stack 30 is driven by the second light emitting signal S_(G),and the third epitaxial stack 40 is driven by the third light emittingsignal S_(B). The first, second, and third light emitting signals S_(R),S_(G), and S_(B) are independently applied to the first, second, andthird epitaxial stacks 20, 30, and 40, and thus, the first, second, andthird epitaxial stacks 20, 30, and 40 may be driven independently ofeach other. The light emitting stacked structure may generate light of acolor, which may be variously determined by a combination of the first,second, and third color lights emitted from the first, second, and thirdepitaxial stacks 20, 30, and 40 in the upper direction.

When displaying a color, different color lights are not emitted fromdifferent planes, but different color lights are emitted from anoverlapping region, and thus, the light emitting stacked structureaccording to an exemplary embodiment is capable of integrating a lightemitting element with reduce size. In general, conventional lightemitting elements emitting different color lights, for example, red,green, and blue lights, are spaced from each other on the same plane toimplement a full color. In this case, as each light emitting element isdisposed on the same plane, the elements occupy a relatively large area.However, light emitting elements according to exemplary embodimentsinclude a stacked structure in which the elements overlap each other inone area to emit different color lights, and thus, a full color may beimplemented in a significantly less area. As such, a high-resolutiondevice may be fabricated in a small area.

In addition, even if a conventional light emitting device was fabricatedin a stack manner, the conventional light emitting device may bemanufactured by forming an individual contact part for a connection withthe individual light emitting element through a line for each lightemitting element, which would increase manufacturing complexities due toa complicated structure. However, the light emitting stacked structureaccording to an exemplary embodiment may be formed by forming a multipleepitaxial stack structure on one substrate, forming a contact part atthe multiple epitaxial stack structure through a minimum process, andconnecting the contact part and the multiple epitaxial stack structure.Also, as compared to a conventional display device fabricating method inwhich a light emitting element of an individual color is fabricated andis individually mounted, according to the inventive concepts, only onelight emitting stacked structure is mounted, instead of a plurality oflight emitting elements, thereby significantly simplifying a fabricatingmethod.

The light emitting stacked structure according to an exemplaryembodiment may further include various elements to provide a high-purityand high-efficiency color light. For example, the light emitting stackedstructure according to an exemplary embodiment may include a wavelengthpass filter for blocking light of a relatively short wavelength fromtraveling toward an epitaxial stack that emits light with a longerwavelength.

Hereinafter, descriptions of a light emitting stacked structureaccording to exemplary embodiments will be focused on a difference fromthat of FIGS. 1 to 2B. In addition, hereinafter, light emitting signalswill be described as being applied to the n-type semiconductor layers21, 31, and 41 of the first, second, and third epitaxial stacks 20, 30,and 40, and a common voltage will be described as being applied to thep-type semiconductor layers 25, 35, and 45 of the first, second, andthird epitaxial stacks 20, 30, and 40, however, the inventive conceptsare not limited thereto.

FIG. 3 is a schematic view a light emitting stacked structure accordingto an exemplary embodiment.

Referring to FIG. 3, a light emitting stacked structure according to anexemplary embodiment may include a first wavelength pass filter 71between the first epitaxial stack 20 and the second epitaxial stack 30.

The first wavelength pass filter 71 may transmit a first color lightemitted from the first epitaxial stack 20 and may block or reflect anyother light except for the first color light. As such, the first colorlight emitted from the first epitaxial stack 20 may travel in the upperdirection, but second and third color light emitted from the second andthird epitaxial stacks 30 and 40 may not travel toward the firstepitaxial stack 20 and may be reflected or blocked by the firstwavelength pass filter 71.

When the second and third color light, which has a higher energy and ashorter wavelength than the first color light, is incident onto thefirst epitaxial stack 20, the second and third color light may induceadditional light emission in the first epitaxial stack 20. In theillustrated exemplary embodiment, the second and third color light isprevented from being incident onto the first epitaxial stack 20 by thefirst wavelength pass filter 71.

A second wavelength pass filter 73 may be provided between the secondepitaxial stack 30 and the third epitaxial stack 40. The secondwavelength pass filter 73 may transmit the first and second color lightemitted from the first and second epitaxial stacks 20 and 30, and mayreflect or block any other light except for the first and second colorlight. As such, the first and second color light emitted from the firstand second epitaxial stacks 20 and 30 may travel in the upper direction,but the third color light emitted from the third epitaxial stack 40 maynot travel toward the first and second epitaxial stacks 20 and 30, andmay be reflected or blocked by the second wavelength pass filter 73.

When the third color light, which has a higher energy and a shorterwavelength than the first and second color light, is incident onto thefirst and second epitaxial stacks 20 and 30, the third color light mayinduce additional light emission of the first and second epitaxialstacks 20 and 30. In the illustrated exemplary embodiment, the thirdcolor light is prevented from being incident onto the first and secondepitaxial stacks 20 and 30 by the second wavelength pass filter 73.

The light emitting stacked structure according to an exemplaryembodiment may further include various elements to provide a uniformlight. For example, the light emitting stacked structure in someexemplary embodiments may have various concavo-convex portions on alight output surface.

FIGS. 4 to 6 are cross-sectional views of a light emitting stackedstructure according to exemplary embodiments.

Referring to FIGS. 4 to 6, the light emitting stacked structureaccording to exemplary embodiments may include a concavo-convex portionPR on an upper surface of an n-type semiconductor layer of at least oneof the first, second, and third epitaxial stacks 20, 30, and 40.

Referring to FIG. 4, the concavo-convex portions PR may be formed on thefirst epitaxial stack 20. Referring to FIG. 5, the concavo-convexportions PR may be respectively provided on the first and thirdepitaxial stacks 20 and 40. Referring to FIG. 6, the concavo-convexportions PR may be respectively provided on the first, second, and thirdepitaxial stacks 20, 30, and 40. In an epitaxial stack including theconcavo-convex portion PR, the concavo-convex portion PR may be providedon an n-type semiconductor layer, which may correspond to a light outputsurface of the epitaxial stack.

The concavo-convex portion PR may be formed in various shapes to improvethe light emitting efficiency, such as a many-sided pyramid, ahemisphere, and rough surfaces arranged randomly. The concavo-convexportion PR may be formed through texturing using various etchingprocesses. Alternatively, the concavo-convex portion PR may be formed byusing a patterned sapphire substrate with concavo-convex portion. Whenthe patterned sapphire substrate is removed from corresponding epitaxialstack, the concavo-convex portion on the patterned sapphire substratemay be transferred to the corresponding epitaxial stack.

In an exemplary embodiment, light emitted from each of the first,second, and third epitaxial stacks 20, 30, and 40 may have differentintensities, which may cause a difference in visibility. According to anexemplary embodiment, the light emission efficiency may be improved byselectively forming the concavo-convex portion PR on light outputsurfaces of the first, second, and third epitaxial stacks 20, 30, and40, thus reducing the difference in visibility with regard to the firstto third color light. For example, a red color and/or a blue color lightmay have lower visibility than a green color light. As such, texturingthe first epitaxial stack 20 and/or the third epitaxial stack 40 mayreduce the difference in visibility between light emitted from theepitaxial stacks. In particular, since an epitaxial stack correspondingto a red light may be disposed on the lowermost of the light emittingstacked structure, the intensity of the red light may be small. As such,the light efficiency may be improved by forming the concavo-convexportion PR on an upper surface of the epitaxial stack emitting the redlight.

The light emitting stacked structure according to an exemplaryembodiment may be formed as a light emitting element, which may expressvarious colors, and thus, the light emitting stacked structure may beadopted as a pixel, which will be described in more detail below.

FIG. 7 is a plan view of a display device according to an exemplaryembodiment, and FIG. 8 is an enlarged plan view of portion P1 of FIG. 7.

Referring to FIGS. 7 and 8, a display device 100 according to anexemplary embodiment may display any visual information, for example, atext, a video, a photo, a two-dimensional or three-dimensional image,etc.

The display device 100 may be provided in various shapes, such as apolygon including straight line segments with closed loop to form aclosed polygonal chain or circuit, a circular, an elliptical, etc.including a curved side, and a semicircular, a semi-elliptical, etc.including a straight or curved side. Hereinafter, the display device 100will be described as having substantially a rectangular shape, but theinventive concepts are not limited thereto.

The display device 100 includes a plurality of pixels 110 displaying animage. Each of the pixels 110 may correspond to a minimum unitdisplaying an image. Each pixel 110 may include the light emittingstacked structure according to exemplary embodiments illustrated withreference to FIGS. 1 to 6, and may emit a white light and/or a colorlight.

In an exemplary embodiment, each pixel 110 includes a first subpixel 110_(R) emitting a red light, a second subpixel 110 _(G) emitting a greenlight, and a third subpixel 110 _(B) emitting a blue light. The first,second, and third subpixels 110 _(R), 110 _(G), and 110 _(E) maycorrespond to the first, second, and third epitaxial stacks 20, 30, and40 of the above-described light emitting stacked structure,respectively.

The pixels 110 are arranged in the matrix of rows and columns. As usedherein, the pixels 110 being arranged in the matrix of rows and columnsmay refer to the pixels 110 being arranged exactly in line along a rowor a column, or substantially arranged along a row or a column in azigzag shape whereby the locations of the pixels 110 may be changed,etc.

FIG. 9 is a block diagram of a display device according to an exemplaryembodiment.

Referring to FIG. 9, the display device 100 according to an exemplaryembodiment includes a timing controller 350, a scan driver unit 310, adata driver unit 330, a wire part, and pixels. When each pixel includesa plurality of subpixels, each subpixel may be connected to the scandriver unit 310, the data driver unit 330, etc., through the wire part.

The timing controller 350 receives various control signals and imagedata from the outside (e.g., an external system which transmits imagedata) to drive the display device 100. The timing controller 350 mayrearrange the received image data and provide the rearranged data to thedata driver unit 330. The timing controller 350 may generate scancontrol signals and data control signals to drive the scan driver unit310 and the data driver unit 330, and provide the generated scan controlsignals and the generated data control signals to the scan driver unit310 and the data driver unit 330.

The scan driver unit 310 may generate a scan signal corresponding to thescan control signal provided from the timing controller 350. The datadriver unit 330 may generate a data signal corresponding to the datacontrol signal and the image data provided from the timing controller350.

The wire part includes a plurality of signal lines. In particular, thewire part includes scan lines 130 _(R), 130 _(G), and 130 _(B)(hereinafter, collectively indicated with reference numeral “130”)connecting the scan driver unit 310 and the subpixels, and data lines120 connecting the data driver unit 330 and the subpixels. The scanlines 130 may be connected to the subpixels of each pixel 110.Accordingly, scan lines connected to the subpixels of each pixel 110 arereferred to as “first, second, and third scan lines 130 _(R), 130 _(G),and 130 _(B)”.

The wire part may connect the timing controller 350 and the scan driverunit 310, the timing controller 350 and the data driver unit 330, or anyother elements, and may include a plurality of lines for transferringrelevant signals that may be used to drive the display device 100.

The scan lines 130 provide scan signals generated by the scan driverunit 310 to the subpixels. Data signals generated by the data driverunit 330 are output to the data lines 120.

The subpixels are connected to the scan lines 130 and the data lines120. The subpixels selectively emit light in response to data signalsreceived from the data lines 120 when scan signals are supplied from thescan lines 130. For example, during each frame period, each subpixelemits light with luminance corresponding to the received data signal. Asubpixel supplied with a data signal corresponding to black luminancemay not emit light during a relevant frame period, thus displaying ablack color.

In an exemplary embodiment, the subpixels may be driven in a passivedriving manner or an active driving manner. When the display device 100is driven in the active driving manner, the display device 100 may bedriven based on first and second pixel voltages additionally suppliedthereto, in addition to a scan signal and a data signal.

FIG. 10 is a circuit diagram illustrating one subpixel according to anexemplary embodiment. In particular, the circuit diagram according tothe illustrated exemplary embodiment may correspond to a subpixel, suchas a red subpixel 110 _(R), included in a passive-type display device.The second and third subpixels 110 _(G) and 110 _(E) may be driven insubstantially the same manner as the first subpixel 110 _(R), and thus,repeated descriptions as to the second and third subpixels 110 _(G) and110 _(E) will be omitted to avoid redundancy.

Referring to FIG. 10, the first subpixel 110 _(R) includes a lightemitting element 150 connected between the first scan line 130 _(R) andthe data line 120. The light emitting element 150 may correspond to thefirst epitaxial stack 20. When a voltage of a threshold voltage orhigher is applied between a p-type semiconductor layer and an n-typesemiconductor layer, the first epitaxial stack 20 emits light withluminance corresponding to the magnitude of the applied voltage. Inparticular, the light emission of the first subpixel 110R may becontrolled by adjusting a voltage of a scan signal applied to the firstscan line 130 _(R) and/or a voltage of a data signal applied to the dataline 120.

FIG. 11 is a circuit diagram illustrating a first subpixel according toan exemplary embodiment. The circuit diagram according to theillustrated exemplary embodiment may correspond to a subpixel includedin an active-type display device.

When the display device 100 is an active-type display device, the firstsubpixel 110R may be further supplied with first and second pixelvoltages ELVDD and ELVSS, as well as a scan signal and a data signal.

Referring to FIG. 11, the first subpixel 110R include at least one lightemitting element 150 and a transistor unit connected to the lightemitting element 150.

The light emitting element 150 may correspond to the first epitaxialstack 20. An n-type semiconductor layer of the light emitting element150 may be connected to the first pixel voltage ELVDD through thetransistor unit, and a p-type semiconductor layer thereof may beconnected to the second pixel voltage ELVSS. The first pixel voltageELVDD and the second pixel voltage ELVSS may have different potentials.For example, a potential of the second pixel voltage ELVSS may be lowerthan a potential of the first pixel voltage ELVDD by not smaller than athreshold voltage of the light emitting element 150. The light emittingelement 150 may emit light with luminance corresponding to a drivingcurrent controlled by the transistor unit.

According to an exemplary embodiment, the transistor unit includes firstand second transistors M1 and M2 and a storage capacitor Cst. However, astructure of the transistor unit may be variously modified and is notlimited to that shown in FIG. 11.

A source electrode of the first transistor M1 (a switching transistor)is connected to the data line 120, and a drain electrode thereof isconnected to a first node N1. A gate electrode of the first transistorM1 is connected to the first scan line 130 _(R). When a scan signal of avoltage enough to turn on the first transistor M1 is supplied from thefirst scan line 130 _(R), the first transistor M1 is turned on, thusconnecting the data line 120 and the first node N1. In this case, a datasignal of a relevant frame is supplied to the data line 120, and thus,the data signal is transferred to the first node N1. The data signaltransferred to the first node N1 is charged in the storage capacitorCst.

A source electrode of the second transistor M2 (a driving transistor) isconnected to the first pixel voltage ELVDD, and a drain electrodethereof is connected to an n-type semiconductor layer. A gate electrodeof the second transistor M2 is connected to the first node N1. Thesecond transistor M2 controls the amount of driving current, which issupplied to the light emitting element 150, based on a voltage of thefirst node N1.

A first end of the storage capacitor Cst is connected to the first pixelvoltage ELVDD, and a second end thereof is connected to the first nodeN1. The storage capacitor Cst charges a voltage corresponding to a datasignal supplied to the first node N1, and maintains the charged voltageuntil a data signal of a next frame is supplied.

Although FIG. 11 shows the transistor unit including two transistors,however, the inventive concepts are not limited thereto, and thestructure of the transistor unit may be variously changed or modified.For example, the transistor unit may include more transistors, morecapacitors, etc. Since the structure of first and second transistors, astorage capacitor, and signal lines are well known in the art, and thus,detailed descriptions thereof will be omitted.

FIG. 12 is a plan view of a pixel according to an exemplary embodiment,and FIG. 13 is a cross-sectional view taken along line I-I′ of FIG. 12.

Referring to FIGS. 12 and 13, a pixel according to an exemplaryembodiment includes a light emitting region, in which a plurality ofepitaxial stacks are stacked, and a peripheral region surrounding thelight emitting region in a plan view. The plurality of epitaxial stacksinclude the first, second, and third epitaxial stacks 20, 30, and 40.

A contact part for connecting a wire part to the first, second, andthird epitaxial stacks 20, 30, and 40 is provided on at least one sideof the light emitting region. The contact part includes a common contactpart 50 c for applying a common voltage to the first, second, and thirdepitaxial stacks 20, 30, and 40, a first contact part 20 c for providinga light emitting signal to the first epitaxial stack 20, a secondcontact part 30 c for providing a light emitting signal to the secondepitaxial stack 30, and a third contact part 40 c for providing a lightemitting signal to the third epitaxial stack 40.

When the light emitting stacked structure has substantially aquadrangular shape in a plan view, the contact parts 20 c, 30 c, 40 c,and 50 c may be disposed in regions corresponding to respective cornersof the quadrangle. However, the inventive concepts are not limitedthereto, and the locations of the contact parts 20 c, 30 c, 40 c, and 50c may be variously changed according to a shape of the light emittingstacked structure.

A common pad electrode 59 c and a common pad 59 p are provided at thecommon contact part 50 c. The common pad electrode 59 c is electricallyconnected to the first, second, and third epitaxial stacks 20, 30, and40 through the first, second, and third p-type contact electrodes 27,37, and 47 by a common bridge electrode 59 b or by a direct contact. Afirst pad electrode 29 c and a first pad 29 p are provided at the firstcontact part 20 c. The first pad electrode 29 c is electricallyconnected with the first epitaxial stack 20 through a first n-typecontact electrode 29.

A second pad electrode 39 c and a second pad 39 p are provided at thesecond contact part 30 c. The second pad electrode 39 c is electricallyconnected with the second epitaxial stack 30 through second bridgeelectrodes 39 b.

A third pad electrode 49 c and a third pad 49 p are provided at thethird contact part 40 c. The third pad electrode 49 c is electricallyconnected with the third epitaxial stack 40 through third bridgeelectrodes 49 b.

The common pad electrode 59 c and the common pad 59 p, the first padelectrode 29 c and the first pad 29 p, the second pad electrode 39 c andthe second pad 39 p, and the third pad electrode 49 c and the third pad49 p, may be provided to overlap each other, and may have substantiallythe same shape and substantially the same area in a plan view. However,the inventive concepts are not limited thereto, and the common padelectrode 59 c and the common pad 59 p, the first pad electrode 29 c andthe first pad 29 p, the second pad electrode 39 c and the second pad 39p, and the third pad electrode 49 c and the third pad 49 p may havevarious shapes and areas. In the illustrated exemplary embodiment, thecommon pad electrode 59 c and the common pad 59 p, the first padelectrode 29 c and the first pad 29 p, the second pad electrode 39 c andthe second pad 39 p, and the third pad electrode 49 c and the third pad49 p will be described as having substantially the same shape andsubstantially the same area to fully overlap each other.

An ohmic electrode 27′ is provided in the light emitting region exceptfor the contact part, so as to overlap the first p-type contactelectrode 27. The ohmic electrode 27′ may be provided to electricallyconnect the first p-type contact electrode 27 and a p-type semiconductorlayer of the first epitaxial stack 20, and may include one or more ohmicelectrodes. For example, as shown in the illustrated exemplaryembodiment, three ohmic electrodes 27′ may be provided. The ohmicelectrode 27′ for an ohmic contact may be formed of various materials.For example, the ohmic electrode 27′ corresponding to a p-type ohmicelectrode may include Au(Zn) or Au(Be). In this case, since reflectanceof a material for the ohmic electrode 27′ is lower than that of amaterial, such as Ag, Al, or Au, an additional reflection electrode maybe further disposed. In particular, Ag, Au, etc. may be used as amaterial for the additional reflection electrode, and a metallicadhesive layer which is formed of a material, such as Ti, Ni, Cr, or Ta,may be disposed for adhesion with an adjacent element. In this case, themetallic adhesive layer may be thinly deposited on an upper surface anda lower surface of a reflection electrode including Ag, Au, etc.

The ohmic electrode 27′ may be disposed in a region spaced apart fromthe first contact part 20 c. For example, the ohmic electrode 27′ may bespaced apart from the first contact part 20 c as much as possible forcurrent spreading. Also, the ohmic electrode 27′ may be disposed in theregion spaced from the second and third contact parts 30 c and 40 c. Assuch, a step, which would otherwise may be formed on a lower portion ofthe light emitting stacked structure upon forming the first, second, andthird pads 29 p, 39 p, and 49 p or when bonded with the substrate 10,may be minimized.

A wire part, which may correspond to the common contact part 50 c andthe first, second, and third contact parts 20 c, 30 c, and 40 c and iselectrically connected with the common pad 59 p and the first, second,and third pads 29 p, 39 p, and 49 p, and/or a driving element, such as athin film transistor, may be further provided on the substrate 10. Inthis case, a common line may be connected to the common pad 59 p, andfirst, second, and third light emitting signal lines may be respectivelyconnected to the first, second, and third pads 29 p, 39 p, and 49 p.

An adhesive layer, a contact electrode, and a wavelength pass filter areprovided between the substrate 10, the first epitaxial stack 20, thesecond epitaxial stack 30, and the third epitaxial stack 40.

In particular, according to an exemplary embodiment, the light emittingstacked structure is provided on the substrate 10, with the firstadhesive layer 60 a interposed therebetween.

The light emitting stacked structure includes the sequentially stackedfirst, second, and third epitaxial stacks 20, 30, and 40, the commoncontact part 50 c and the first, second, and third contact parts 20 c,30 c, and 40 c connected to the first, second, and third epitaxialstacks 20, 30, and 40. The wire part may be formed on the substrate 10,and the common contact part 50 c and the first, second, and thirdcontact parts 20 c, 30 c, and 40 c may electrically connect the commoncontact part 50 c and the first, second, and third contact parts 20 c,30 c, and 40 c with the wire part of the substrate 10 through aconductive adhesive layer 61.

The conductive adhesive layer 61 may include a conductive paste, such asa solder paste or a silver paste, a conductive resin, or an anisotropicconductive film.

When the substrate 10 does not include the conductive adhesive layer 61,the first adhesive layer 60 a for attaching the light emitting stackedstructure to the substrate 10 may be provided between the substrate 10and the light emitting stacked structure.

The first epitaxial stack 20 is provided on the lowermost portion of thelight emitting stacked structure. A partial region of the firstepitaxial stack 20 may have a mesa structure protruding toward a lowerside and being depressed toward an upper side. In particular, portionsof a p-type semiconductor layer, an active layer, and an n-typesemiconductor layer of the first epitaxial stack 20 may be removed toexpose the n-type semiconductor layer in the lower direction. A portionwhich is depressed by removing portions of the p-type semiconductorlayer, the active layer, and the n-type semiconductor layer of the firstepitaxial stack 20 may be hereinafter be referred to as a “recess”, anda portion where a mesa is formed may be referred to as a “protrusion”.In this case, in a plan view, the recess is provided within a regioncorresponding to the first contact part 20 c, in detail, a region wherethe first pad 29 p is formed. In an exemplary embodiment, the size ofthe recess may be smaller than the size of the first pad 29 p tominimize a step, which may be formed upon bonding the light emittingstacked structure and the substrate 10 to be discussed later.

A first insulating layer 81 is disposed on a lower surface of the firstepitaxial stack 20, in particular, a surface of the first epitaxialstack 20 that faces the substrate 10. A plurality of contact holes areformed in the first insulating layer 81. The contact holes arerespectively provided in the regions of the first insulating layer 81,which correspond to the recess and the protrusion.

The first n-type contact electrode 29, which contacts the n-typesemiconductor layer of the first epitaxial stack 20, is provided in thecontact hole corresponding to the recess. The ohmic electrode 27′, whichcontacts the p-type semiconductor layer of the first epitaxial stack 20,is provided in the contact hole corresponding to the protrusion.

The first n-type contact electrode 29 may be formed of variousconductive materials, and may be formed of at least one of variousmetals and an alloy thereof. In an exemplary embodiment, the firstn-type contact electrode 29 may be formed of an Au alloy, such as AuGeor AuTe. The first p-type ohmic electrode 27′ may include Au(Zn) orAu(Be). Here, since reflectance of a material for the ohmic electrode27′ is lower than that of a material, such as Ag, Al, or Au, anadditional reflection electrode may be further disposed. In an exemplaryembodiment, Ag, Au, etc. may be used as a material for an additionalreflection electrode, and a metallic adhesive layer formed of a materialsuch as Ti, Ni, Cr, or Ta may be disposed for adhesion with an adjacentelement. In this case, the adhesive layer may be thinly deposited on anupper surface and a lower surface of the reflection electrode includingAg, Au, etc. However, the inventive concepts are not limited thereto,and the first n-type contact electrode 29 or the ohmic electrode 27′ maybe formed with various other materials.

The first p-type contact electrode 27, the common pad electrode 59 c,and the first, second, and third pad electrodes 29 c, 39 c, and 49 c areprovided on the ohmic electrode 27′ and the first insulating layer 81.The common pad electrode 59 c is provided at the common contact part 50c, and the first, second, and third pad electrodes 29 c, 39 c, and 49 care respectively provided at the first, second, and third contact parts20 c, 30 c, and 40 c. Here, the first p-type contact electrode 27 andthe common pad electrode 59 c may be integrally formed, and contact theohmic electrode 27′ for electrical connection.

The first p-type contact electrode 27 may be formed of a material havinga reflectivity to reflect light emitted from the first epitaxial stack20. The first insulating layer 81 may have reflectivity to assistreflection of light emitted from the first epitaxial stack 20. Forexample, the first insulating layer 81 may have an omni-directionalreflector (ODR) structure.

The common pad electrode 59 c and the first, second, and third padelectrodes 29 c, 39 c, and 49 c are spaced from each other, and thus,are electrically/physically insulated from each other. The common padelectrode 59 c and the first, second, and third pad electrodes 29 c, 39c, and 49 c may have a size enough to cover regions corresponding to thecommon contact part 50 c and the first, second, and third contact parts20 c, 30 c, and 40 c, respectively. Also, the common pad electrode 59 cand the first, second, and third pad electrodes 29 c, 39 c, and 49 c mayinclude substantially the same material and disposed on the same layer.

In particular, the first pad electrode 29 c covers the regioncorresponding to the first contact part 20 c and formed to be largerthan the recess of the first epitaxial stack 20. Also, the second andthird pad electrodes 39 c and 49 c and the common pad electrode 59 c maycover the regions respectively corresponding to the second contact part30 c, the third contact part 40 c, and the common contact part 50 c, andmay be provided to have a size identical or similar to the size of thefirst pad electrode 29 c. As the size of the first pad electrode 29 c islarger than the size of the recess, the influence of the step due to therecess upon forming the first pad 29 p later may be minimized. Inaddition to the first pad electrode 29 c, also, the second and third padelectrodes 39 c and 49 c and the common pad electrode 59 c may beprovided on the same insulating layer with substantially the sameheight, and may be provided with the sufficient large area, even thougha contact with bridge electrodes (to be described later) connected tothe second and third pads 39 p and 49 p and the common pad 59 p may beformed narrowly. As such, the step that may be formed on a back surfaceof the first epitaxial stack 20 due to the first, second, and third padelectrodes 29 c, 39 c, and 49 c and the common pad electrode 59 c may beminimized.

A second insulating layer 83 is provided on the back surface of thefirst epitaxial stack 20, to which the first, second, and third padelectrodes 29 c, 39 c, and 49 c and the common pad electrode 59 c areformed. The second insulating layer 83 includes contact holes at regionscorresponding to the common contact part 50 c and the first, second, andthird contact parts 20 c, 30 c, and 40 c. Portions of lower surfaces ofthe common pad electrode 59 c and the first, second, and third padelectrodes 29 c, 39 c, and 49 c are exposed through the contact holesformed in the second insulating layer 83. The contact holes of thesecond insulating layer 83 may be formed to be smaller than the commonpad electrode 59 c and the first, second, and third pad electrodes 29 c,39 c, and 49 c.

The common pad 59 p and the first, second, and third pads 29 p, 39 p,and 49 p are provided under the second insulating layer 83. The commonpad 59 p is disposed on the common contact part 50 c and is connected tothe common pad electrode 59 c through a contact hole. The first, second,and third pads 29 p, 39 p, and 49 p are respectively disposed on thefirst, second, and third contact parts 20 c, 30 c, and 40 c, and arerespectively connected to the first, second, and third pad electrodes 29c, 39 c, and 49 c through the contact holes. The common pad 59 p and thefirst, second, and third pads 29 p, 39 p, and 49 p protrude in the lowerdirection from a lower surface of the second insulating layer 83. Theconductive adhesive layers 61 are respectively provided on lowersurfaces of the common pad 59 p and the first, second, and third pads 29p, 39 p, and 49 p, such that the common pad 59 p and the first, second,and third pads 29 p, 39 p, and 49 p are attached to the substrate 10.The first adhesive layer 60 a is provided between the substrate 10 andthe second insulating layer 83, where the common pad 59 p and the first,second, and third pads 29 p, 39 p, and 49 p are not provided.

A third insulating layer 85 is provided on an upper surface of the firstepitaxial stack 20. The first epitaxial stack 20 has contact holesvertically penetrating at the common contact part 50 c and the secondand third contact parts 30 c and 40 c. Portions of upper surfaces of thecommon pad electrode 59 c and the second and third pad electrodes 39 cand 49 c are exposed by the contact holes in the first epitaxial stack20. The common bridge electrode 59 b connecting the common pad electrode59 c and the second and third epitaxial stacks 30 and 40, a secondbridge electrode 39 b connecting the second pad electrode 39 c and thesecond epitaxial stack 30, and a third bridge electrode 49 b connectingthe third pad electrode 49 c and the third epitaxial stack 40 areprovided in the contact holes of the first epitaxial stack 20. The thirdinsulating layer 85 for insulation from the first epitaxial stack 20 isprovided on inner side walls of the contact holes.

The second adhesive layer 60 b is provided on the first epitaxial stack20, and the third insulating layer 85, and the first wavelength passfilter 71, the second p-type contact electrode 37, the second epitaxialstack 30, and a fourth insulating layer 87 are sequentially provided onthe second adhesive layer 60 b. The second epitaxial stack 30 mayinclude a p-type semiconductor layer, an active layer, and an n-typesemiconductor layer stacked in the upper direction from the bottom.

The first wavelength pass filter 71, the second p-type contact electrode37, the second epitaxial stack 30, and the fourth insulating layer 87have contact holes vertically penetrating at the common contact part 50c and the second and third contact parts 30 c and 40 c.

In the common contact part 50 c, the first wavelength pass filter 71 andthe second p-type contact electrode 37 have contact holes having a firstdiameter, and the second epitaxial stack 30 and the fourth insulatinglayer 87 have contact holes having a second diameter greater than thefirst diameter. The fourth insulating layer 87 is provided on side wallsof all the contact holes, and thus, the common bridge electrodes 59 bformed in the contact holes are insulated from elements disposed aroundthe contact holes. However, since the contact hole in the secondepitaxial stack 30 has a diameter greater than a diameter of a lowercontact hole, a portion of an upper surface of the second p-type contactelectrode 37 is exposed in the contact hole having the greater diameter.The common bridge electrode 59 b is provided in the contact holeprovided at the common contact part 50 c, and thus, the common bridgeelectrode 59 b and the second p-type contact electrode 37 may directlycontact each other and be connected.

In the second contact part 30 c, the first wavelength pass filter 71,the second p-type contact electrode 37, the second epitaxial stack 30,and the fourth insulating layer 87 have contact holes that havesubstantially the same diameter. A contact hole formed in the fourthinsulating layer 87 may expose an upper surface of the second epitaxialstack 30 along an outer surface of the contact hole. Since the secondbridge electrode 39 b is provided in the contact hole, the second bridgeelectrode 39 b covers a portion of an upper surface of the secondepitaxial stack 30, in particular, the contact hole of the fourthinsulating layer 87 provided on the second epitaxial stack 30. As such,the second bridge electrode 39 b may directly contact an upper portionof the second epitaxial stack 30 and be connected therewith. The upperportion of the second epitaxial stack 30 may correspond to an n-typesemiconductor layer. The fourth insulating layer 87 is provided on sidewalls of the contact holes provided in the first wavelength pass filter71, the second p-type contact electrode 37, the second epitaxial stack30, and the fourth insulating layer 87, and thus, the second bridgeelectrode 39 b provided therein is insulated from elements disposedaround the contact holes.

In the third contact part 40 c, the first wavelength pass filter 71, thesecond p-type contact electrode 37, the second epitaxial stack 30, andthe fourth insulating layer 87 have contact holes having substantiallythe same diameter. The fourth insulating layer 87 is provided on sidewalls of the contact holes provided in the first wavelength pass filter71, the second p-type contact electrode 37, the second epitaxial stack30, and the fourth insulating layer 87, and thus, the second bridgeelectrodes 39 b provided therein are insulated from elements disposedaround the contact holes.

The third adhesive layer 60 c is provided on the second epitaxial stack30. The second wavelength pass filter 73, the third p-type contactelectrode 47, the third epitaxial stack 40, and a fifth insulating layer89 are sequentially provided on the third adhesive layer 60 c. The thirdepitaxial stack 40 may include a p-type semiconductor layer, an activelayer, and an n-type semiconductor layer stacked in the upper directionfrom the bottom.

The second wavelength pass filter 73, the third p-type contact electrode47, the third epitaxial stack 40, and the fifth insulating layer 89 havecontact holes vertically penetrating at the common contact part 50 c andthe third contact part 40 c. A contact hole is not provided at thesecond wavelength pass filter 73, the third p-type contact electrode 47,the third epitaxial stack 40, and the fifth insulating layer 89corresponding to the second contact part 30 c.

In the common contact part 50 c, the second wavelength pass filter 73and the third p-type contact electrode 47 have contact holes having athird diameter, and the third epitaxial stack 40 and the fifthinsulating layer 89 have contact holes having a fourth diameter greaterthan the third diameter. The fifth insulating layer 89 is provided onside walls of all the contact holes, and thus, the common bridgeelectrodes 59 b provided therein are insulated from elements disposedaround the contact holes. However, as a contact hole formed in the thirdepitaxial stack 40 has a diameter greater than a diameter of a lowercontact hole, a portion of an upper surface of the third p-type contactelectrode 47 is exposed in the contact hole having the greater diameter.The common bridge electrode 59 b is provided in the contact holeprovided at the common contact part 50 c, and thus, the common bridgeelectrode 59 b and the third p-type contact electrode 47 may directlycontact each other and be connected.

In the third contact part 40 c, the second wavelength pass filter 73,the third p-type contact electrode 47, the third epitaxial stack 40, andthe fifth insulating layer 89 have contact holes having substantiallythe same diameter. The fifth insulating layer 89 has a contact holewhich exposes an upper surface of the third epitaxial stack 40 along anouter surface of the contact hole. Since the third bridge electrode 49 bis provided in the contact hole, the third bridge electrode 49 b coversa portion of an upper surface of the third epitaxial stack 40, inparticular, the contact hole of the fifth insulating layer 89 providedon the third epitaxial stack 40. As such, the third bridge electrode 49b may directly contact an upper portion of the third epitaxial stack 40and be connected therewith. The upper portion of the third epitaxialstack 40 may correspond to an n-type semiconductor layer. The fifthinsulating layer 89 is provided on side walls of the contact holesprovided in the second wavelength pass filter 73, the third p-typecontact electrode 47, the third epitaxial stack 40, and the fifthinsulating layer 89, and thus, the third bridge electrodes 49 b providedtherein are insulated from elements disposed around the contact holes.

The first, second, third, fourth, and fifth insulating layers 81, 83,85, 87, and 89 may be formed of a various organic/inorganic insulationmaterials, but the inventive concepts are not limited to a particularmaterial forming the insulating layers. For example, the first, second,third, fourth, and fifth insulating layers 81, 83, 85, 87, and 89 may beformed of an inorganic insulation material including silicon nitride,silicon oxide, etc., or organic insulation materials includingpolyimide.

In an exemplary embodiment, a concavo-convex portion may be selectivelyprovided on an upper surface of each of the first, second, and thirdepitaxial stacks 20, 30, and 40, in particular, an upper surface of eachof n-type semiconductor layers of the first, second, and third epitaxialstacks 20, 30, and 40. The concavo-convex portion may be provided onlyin a portion corresponding to a light emitting region, or may beprovided on the entire upper surface of each n-type semiconductor layer.

In some exemplary embodiments, the fifth insulating layer 89 may beprovided on a side surface of the light emitting stacked structure, andan additional light-opaque layer may be further provided in addition tothe fifth insulating layer 89. The light-opaque layer may be a lightblocking layer for preventing lights from the first, second, and thirdepitaxial stacks 20, 30, and 40 from being output toward sides of thelight emitting stacked structure, and may include a material whichabsorbs a light or reflects a light. The light-opaque layer is notspecifically limited as long as it absorbs or reflects light. In anexemplary embodiment, the light-opaque layer may be a distributed Braggreflector (DBR) dielectric mirror or a metallic reflection layer formedon an insulating layer, or may be an organic polymer layer of a blackcolor. When the metallic reflection layer is used as the light-opaquelayer, the metallic reflection layer may be electrically insulated froman element of other light emitting stacked structure.

When the light-opaque layer is provided on a side surface of the lightemitting stacked structure, it may be possible to prevent light emittedfrom a particular light emitting stacked structure from having aninfluence on an adjacent light emitting stacked structure, or to preventa color mixing phenomenon that may occur between adjacent light emittingstacked structures.

In the light emitting stacked structure according to an exemplaryembodiment, a common voltage is applied to the first, second, and thirdepitaxial stacks 20, 30, and 40 through the common pad electrode 59 c,and first, second, and third light emitting signals are respectivelyapplied to the first, second, and third epitaxial stacks 20, 30, and 40through the first, second, and third pad electrodes 29 c, 39 c, and 49c. In particular, the common pad electrode 59 c is electricallyconnected to a p-type semiconductor layer of the first epitaxial stack20 through the first p-type contact electrode 27 and the ohmic electrode27′, electrically connected to a p-type semiconductor layer of thesecond epitaxial stack 30 through the common bridge electrode 59 b andthe second p-type contact electrode 37, and electrically connected to ap-type semiconductor layer of the third epitaxial stack 40 through thecommon bridge electrode 59 b and the third p-type contact electrode 47.The first pad electrode 29 c is electrically connected to an n-typesemiconductor layer of the first epitaxial stack 20 through the firstn-type contact electrode 29, the second pad electrode 39 c iselectrically connected to an n-type semiconductor layer of the secondepitaxial stack 30 through the second bridge electrode 39 b, and thethird pad electrode 49 c is electrically connected to an n-typesemiconductor layer of the third epitaxial stack 40 through the thirdbridge electrode 49 b.

In this manner, as the common voltage is applied to the common contactpart 50 c and the light emitting signal are respectively applied to thefirst, second, and third epitaxial stacks 20, 30, and 40, the first,second, and third epitaxial stacks 20, 30, and 40 may be independentlycontrolled to emit light, and thus, a color may be variously implementeddepending on whether each epitaxial stack emits light.

The light emitting stacked structure according to an exemplaryembodiment may be fabricated by sequentially stacking the first, second,and third epitaxial stacks 20, 30, and 40 on the substrate 10, whichwill be described below.

FIGS. 14, 16, 18, 20, 22, 24, 26, 28, 30, and 32 are plan viewsillustrating a method of forming the first, second, and third epitaxialstacks 20, 30, and 40 on the substrate 10. FIGS. 15A, 15B, 17, 19A and19B, 21, 23, 25A and 25B, 27A and 27B, 29, 31A to 31E, and 33A to 33Eare cross-sectional views taken along line I-I′ of FIGS. 14, 16, 18, 20,22, 24, 26, 28, 30, and 32.

Referring to FIGS. 14 and 15A, the first epitaxial stack 20 is formed ona first temporary substrate 10 p. In an exemplary embodiment, the firsttemporary substrate 10 p may be a semiconductor substrate for formingthe first epitaxial stack 20, and may be, for example, a GaAs substrate.The first epitaxial stack 20 may be formed to have a mesa structureincluding a recess RC and a protrusion PTR, which may be formed byforming an n-type semiconductor layer, an active layer, and a p-typesemiconductor layer on the first temporary substrate 10 p and removingportions of the n-type semiconductor layer, the active layer, and thep-type semiconductor layer. The recess RC is provided in a regioncorresponding to the first contact part 20 c, and may be formed to besmaller than the first pad electrode 29 c or the first pad 29 p to beformed later, to reduce a step with any other region except for theregion where the recess RC will be formed.

Referring to FIGS. 14 and 15B, the first insulating layer 81 is formedon the first epitaxial stack 20 where the mesa structure is formed, andthe ohmic electrode 27′ is formed on the p-type semiconductor layer.

The ohmic electrode 27′ according to an exemplary embodiment may beformed through the following processes: forming an insulating layer onthe first epitaxial stack 20 through deposition, coating a photoresist,patterning the photoresist through exposure and development, forming acontact hole through wet etching or dry etching by using the photoresistpattern as a mask, depositing an ohmic electrode layer on a frontsurface of the first epitaxial stack 20 on which the photoresist patternis provided, and lifting off the photoresist pattern. In an exemplaryembodiment, the ohmic electrode 27′ may be formed by depositing at leastone of AuBe and Au layers.

Referring to FIGS. 16 and 17, the first n-type contact electrode 29 isformed on the first insulating layer 81. The first n-type contactelectrode 29 may be provided in the recess, and a diameter of the firstn-type contact electrode 29 may be smaller than a diameter of therecess.

The first n-type contact electrode 29 according to an exemplaryembodiment may be formed through the following processes: coating aphotoresist, patterning the photoresist through exposure anddevelopment, forming a contact hole through wet etching or dry etchingby using the photoresist pattern as a mask, depositing a material forthe first n-type contact electrode 29 on a front surface of the firstepitaxial stack 20 on which the photoresist pattern is provided, andlifting off the photoresist pattern. In an exemplary embodiment, thefirst n-type contact electrode 29 may be formed by depositing an AuGelayer.

Referring to FIGS. 18 and 19A, the common pad electrode 59 c, the firstp-type contact electrode 27, and the first, second, and third padelectrodes 29 c, 39 c, and 49 c are formed on the first insulating layer81 in which the ohmic electrode 27′ and the first n-type contactelectrode 29 are formed. Here, the common pad electrode 59 c and thefirst p-type contact electrode 27 may be integrally formed.

The common pad electrode 59 c, the first p-type contact electrode 27,and the first, second, and third pad electrodes 29 c, 39 c, and 49 c maybe formed by depositing a conductive material and patterning thedeposited conductive material by using photolithography, for example.

Referring to FIGS. 18 and 19B, the second insulating layer 83 is formedon the common pad electrode 59 c, the first p-type contact electrode 27,and the first, second, and third pad electrodes 29 c, 39 c, and 49 c.The second insulating layer 83 may be formed to have a thickness enoughto compensate for a step between a recess and a protrusion. After thesecond insulating layer 83 is formed with a sufficient thickness,planarization may be performed to smooth a surface of the secondinsulating layer 83. The planarization may be performed by using CMP orthe like.

Referring to FIGS. 20 and 21, contact holes are respectively formed atthe first, second, and third contact parts 20 c, 30 c, and 40 c, and thecommon contact part 50 c by patterning the second insulating layer 83.The contact holes formed at the first, second, and third contact parts20 c, 30 c, and 40 c, and the common contact part 50 c expose portionsof upper surfaces of the first, second, and third pad electrodes 29 c,39 c, and 49 c, and the common pad 59 c.

Referring to FIGS. 22 and 23, the common pad 59 p and the first, second,and third pads 29 p, 39 p, and 49 p are formed on the first epitaxialstack 20 on which the second insulating layer 83 is formed. In anexemplary embodiment, the common pad electrode 59 c and the first,second, and third pad electrodes 29 c, 39 c, and 49 c may be formed in asingle process, and thus, may include substantially the same material onthe same layer.

The common pad 59 p and the first, second, and third pads 29 p, 39 p,and 49 p may be provided in regions corresponding to the common contactpart 50 c and the first, second, and third contact parts 20 c, 30 c, and40 c, and may be formed to cover the regions corresponding to the commoncontact part 50 c and the first, second, and third contact parts 20 c,30 c, and 40 c. As the common pad 59 p and the first, second, and thirdpads 29 p, 39 p, and 49 p are formed as wide as possible, heat generatedfrom each epitaxial stack may be easily dissipated, and reduce thepossibility of misalignment when bonded to the substrate. Also, sincethe first pad 29 p is formed to be larger than the region where therecess is formed, a defect in adhesion due to a step of the recess maybe prevented.

The common pad 59 p and the first, second, and third pads 29 p, 39 p,and 49 p may be formed of a conductive material, and may include, forexample, various metals, such as Al, Ti, Cr, Ni, Au, Ag, Ti, Sn, Ni, Cr,W, and Cu, or an alloy thereof. Also, the common pad 59 p and the first,second, and third pads 29 p, 39 p, and 49 p may be formed in a singlelayer or a multi-layer. When the common pad 59 p and the first, second,and third pads 29 p, 39 p, and 49 p are formed as a multi-layer, abarrier metal layer may be added to prevent a particular metal frombeing diffused. In an exemplary embodiment, the common pad 59 p and thefirst, second, and third pads 29 p, 39 p, and 49 p may be formed ofAuSn, and a barrier layer including Cr, Ti, Ni, W, or an alloy thereofmay be added between the pads 59 p, 29 p, 39 p, and 49 p, and theelectrodes 50 c, 29 c, 39 c, and 49 c to prevent diffusion of Sn.

Referring to FIGS. 24, 25A, and 25B, the first epitaxial stack 20 formedon the first temporary substrate 10 p may be inverted and attached onthe substrate 10, on which the first adhesive layer 60 a is formed. Assuch, layers of the first epitaxial stack 20 are disposed on the uppersurface of the substrate 10, in the order of a p-type semiconductorlayer, an active layer, and an n-type semiconductor layer.

The conductive adhesive layers 61 are formed at regions of the substrate10 to correspond to the common pad 59 p and the first, second, and thirdpads 29 p, 39 p, and 49 p. The first temporary substrate 10 p may bepressed in the lower direction from the top after aligning the commonpad 59 p and the first, second, and third pads 29 p, 39 p, and 49 p tothe first temporary substrate 10 p to face the conductive adhesivelayers 61, as shown in FIG. 25B.

Referring to FIGS. 26 and 27A, contact holes are formed by removingportions of the first epitaxial stack 20 and the first insulating layer81. Contact holes are respectively formed at the common contact part 50c and the second and third contact parts 30 c and 40 c, and thus,portions of upper surfaces of the common pad electrode 59 c and thesecond and third pad electrodes 39 c and 49 c are exposed.

Referring to FIGS. 26 and 27B, the third insulating layer 85 is formedon the first epitaxial stack 20. The third insulating layer 85 is formedon an upper surface of the first epitaxial stack 20 and side surfaces ofthe contact holes, and thus, portions of upper surfaces of the commonpad electrode 59 c and the second and third pad electrodes 39 c and 49 cremain exposed.

The third insulating layer 85 may be formed by forming a layer includingan insulating material on an upper surface of the first epitaxial stack20, and anisotropically etching the interior of the contact holes byusing photolithography.

Although the contact holes formed in the first epitaxial stack 20 areillustrated as having a sufficient diameter, however, an actual diameterof each contact hole may be very small, which makes forming the thirdinsulating layer 85 only on an inner side surface of each contact holedifficult when the third insulating layer 85 is formed to have asufficient thickness on the upper surface of the first epitaxial stack20. In some exemplary embodiments, a process of forming an additionalsub-insulating layer may be used to make it easier to form the thirdinsulating layer 85 on an inner side surface of each contact hole, asdescribed in more detail below.

FIGS. 34A to 34D are enlarged cross-sectional views illustrating aportion corresponding to P2 of FIG. 27A, which sequentially show aprocess of forming the third insulating layer 85 in a contact hole,according to another exemplary embodiment. It is noted that the processof forming an insulating layer in a contact hole shown in FIGS. 34A to34C may be applied to forming an insulating layer in a contact hole forany other epitaxial layer.

Referring to FIG. 34A, a first sub-insulating layer 85 a is formed on anupper surface of the first epitaxial stack 20 before forming a contacthole. Referring to FIG. 34B, an upper surface of the second padelectrode 39 c is exposed by etching the first sub-insulating layer 85 aand the first epitaxial stack 20. Referring to FIG. 34C, a secondsub-insulating layer 85 b is formed on the first epitaxial stack 20 andthe first sub-insulating layer 85 a where the contact hole is formed.Referring to FIG. 34D, the upper surface of the second pad electrode 39c is exposed again by etching the second sub-insulating layer 85 b. Assuch, only the second sub-insulating layer 85 b is formed on an innerside surface of the contact hole, and the first and secondsub-insulating layers 85 a and 85 b are formed on the upper surface ofthe first epitaxial stack 20. In the manner, since a thickness of afinal insulating layer 85 provided on the upper surface of the firstepitaxial stack 20 is greater than a thickness of an insulating layerprovided on an inner side surface of a contact hole, it is possible toform an insulating layer that is thin enough to cover the inner sidesurface of the contact hole, while having a sufficient thickness on theupper surface of the first epitaxial stack 20.

Referring back to FIG. 27B, an upper surface of the first epitaxialstack 20 and an inner side surface of a contact hole are covered by thethird insulating layer 85 as described above.

Referring to FIGS. 28 and 29, the common bridge electrode 59 b and thesecond and third bridge electrodes 39 b and 49 b are formed on the firstepitaxial stack 20, on which the third insulating layer 85 is formed.The common bridge electrode 59 b is connected with the common padelectrode 59 c through the contact hole, the second bridge electrode 39b is connected with the second pad electrode 39 c through the contacthole, and the third bridge electrode 49 b is connected with the thirdpad electrode 49 c through the contact hole.

Referring to FIGS. 30 and 31A, the second epitaxial stack 30 is formedon a second temporary substrate, and the second epitaxial stack 30 maybe inverted and attached on the first epitaxial stack 20 with the secondadhesive layer 60 b interposed therebetween. According to an exemplaryembodiment, the second p-type contact electrode 37 and the firstwavelength pass filter 71 may be formed between the second adhesivelayer 60 b and the second epitaxial stack 30. The second temporarysubstrate may be removed after the second epitaxial stack 30 is attachedon the first epitaxial stack 20. The second temporary substrate may beremoved through various methods. For example, when the second temporarysubstrate is a sapphire substrate, the sapphire substrate may be removedby a laser lift-off method, a stress lift-off method, a mechanicallift-off method, a physical polishing method, etc.

In some exemplary embodiments, after the second temporary substrate isremoved, the concavo-convex portion PR may be formed on an upper surface(or on an n-type semiconductor layer) of the second epitaxial stack 30.The concavo-convex portion PR may be formed through texturing usingvarious etching processes. Alternatively, the concavo-convex portion PRmay be formed by using a patterned sapphire substrate withconcavo-convex portion as a temporary substrate. When the patternedsapphire substrate is removed from corresponding epitaxial stack, theconcavo-convex portion on the patterned sapphire substrate istransferred to the corresponding epitaxial stack. In some exemplaryembodiments, a concavo-convex portion may be formed through variousother methods, such as dry etching using a micro photo process, wetetching using a crystalline property, texturing using a physical methodsuch as sandblast, ion beam etching, and texturing using an etchingspeed difference of block copolymer.

Referring to FIGS. 30 and 31B, contact holes are formed by removingportions of the second epitaxial stack 30. The contact holes arerespectively formed at the common contact part 50 c and the second andthird contact parts 30 c and 40 c, and thus, portions of an uppersurface of the second p-type contact electrode 37 are exposed. Thesecond p-type contact electrode 37 may be formed with a sufficientthickness and function as an etch stopper.

Referring to FIGS. 30 and 31C, additional contact holes are formed inthe contact holes by removing portions of the second p-type contactelectrode 37, the first wavelength pass filter 71, and the secondadhesive layer 60 b that correspond to the common contact part 50 c andthe second and third contact parts 30 c and 40 c. Portions of uppersurfaces of the common bridge electrode 59 b, the second bridgeelectrode 39 b, and the third bridge electrode 49 b are exposed by thecontact holes.

In this case, the additional contact hole formed at the common contactpart 50 c may have a diameter smaller than the contact hole formed inthe second epitaxial stack 30. More particularly, assuming that acontact hole formed by removing a portion of the second epitaxial stack30 is referred to as an “upper contact hole” and a contact hole formedby removing portions of the second p-type contact electrode 37, thefirst wavelength pass filter 71, and the second adhesive layer 60 b isreferred to as a “lower contact hole”, a diameter of the upper contacthole is greater than a diameter of the lower contact hole. As such,after contact holes are formed, an upper surface of the second p-typecontact electrode 37 is exposed due to a greater diameter of the uppercontact hole.

Referring to FIGS. 30 and 31D, the fourth insulating layer 87 is formedon the second epitaxial stack 30 in which the contact holes are formed.The fourth insulating layer 87 is formed to cover an upper surface ofthe second epitaxial stack 30 and a side surface of each contact hole.

The fourth insulating layer 87 is etched to expose portions of uppersurfaces of the common bridge electrode 59 b, the second bridgeelectrode 39 b, and the third bridge electrode 49 b. In addition, acontact hole is formed in the fourth insulating layer 87 to exposes aportion of an upper surface of the second epitaxial stack 30 thatcorresponds to the second contact part 30 c.

Referring to FIGS. 30 and 31E, the common bridge electrode 59 b, thesecond bridge electrode 39 b, and the third bridge electrode 49 b areformed on the second epitaxial stack 30 on which the fourth insulatinglayer 87 is formed. The common bridge electrode 59 b may directlycontact the exposed second p-type contact electrode 37. Also, the secondbridge electrode 39 b is formed to cover a contact hole in the fourthinsulating layer 87 that exposes a portion of an upper surface of thesecond epitaxial stack 30 at a region corresponding to the secondcontact part 30 c. In this manner, the second bridge electrode 39 b maydirectly contact the upper surface of the second epitaxial stack 30.

Referring to FIGS. 32 and 33A, the third epitaxial stack 40 is formed ona third temporary substrate, and the third epitaxial stack 40 may beinverted and attached on the second epitaxial stack 30 with the thirdadhesive layer 60 c interposed therebetween. According to an exemplaryembodiment, the third p-type contact electrode 47 and the secondwavelength pass filter 73 may be formed between the third epitaxialstack 40 and the third adhesive layer 60 c. The third temporarysubstrate may be removed after the third epitaxial stack 40 is attachedon the second epitaxial stack 30. The third temporary substrate may beremoved through substantially the same process for removing the secondtemporary substrate described above.

In some exemplary embodiments, after the third temporary substrate isremoved, the concavo-convex portion PR may be formed on an upper surface(or on an n-type semiconductor layer) of the third epitaxial stack 40.

Referring to FIGS. 32 and 33B, contact holes are formed in the thirdepitaxial stack 40 by removing portions of the third epitaxial stack 40.The contact holes are respectively formed at the common contact part 50c and the third contact part 40 c, and thus, portions of an uppersurface of the third p-type contact electrode 47 are exposed. The thirdp-type contact electrode 47 may be formed with a sufficient thicknessand function as an etch stopper.

Referring to FIGS. 32 and 33C, contact holes are formed in the thirdp-type contact electrode 47, the second wavelength pass filter 73, andthe third adhesive layer 60 c by removing regions that correspond to thecommon contact part 50 c and the third contact part 40 c. As such,portions of upper surfaces of the common bridge electrode 59 b, thesecond bridge electrode 39 b, and the third bridge electrode 49 b areexposed by the contact holes.

The contact hole formed in the third p-type contact electrode 47, thesecond wavelength pass filter 73, and the third adhesive layer 60 c ofthe common contact part 50 c has a diameter smaller a contact holeformed in the third epitaxial stack 40. As such, after contact holes areformed, an upper surface of the third p-type contact electrode 47 isexposed due to a greater diameter of the upper contact hole.

Referring to FIGS. 32 and 33D, the fifth insulating layer 89 is formedon the third epitaxial stack 40 in which the contact holes are formed.The fifth insulating layer 89 is formed to cover an upper surface of thethird epitaxial stack 40 and a side surface of each contact hole.

The fifth insulating layer 89 is etched to expose portions of uppersurfaces of the common bridge electrode 59 b, the second bridgeelectrode 39 b, and the third bridge electrode 49 b. A contact hole isformed in the fifth insulating layer 89 to expose a portion of an uppersurface of the third epitaxial stack 40 in a region corresponding to thethird contact part 40 c.

Referring to FIGS. 32 and 33E, the common bridge electrode 59 b, thesecond bridge electrode 39 b, and the third bridge electrode 49 b areformed on the third epitaxial stack 40 on which the fifth insulatinglayer 89 is formed. The common bridge electrode 59 b may directlycontact the exposed third p-type contact electrode 47. Also, the thirdbridge electrode 49 b is formed to cover a contact hole exposing aportion of an upper surface of the third epitaxial stack 40 at a regioncorresponding to the third contact part 40 c, and thus, the third bridgeelectrode 49 b may directly contact the upper surface of the thirdepitaxial stack 40.

In some exemplary embodiments, the fifth insulating layer 89 may beprovided on a side surface of the light emitting stacked structure, andan additional light-opaque layer may be further provided in addition tothe fifth insulating layer 89. The light-opaque layer may be a lightblocking layer for preventing lights from the first, second, and thirdepitaxial stacks 20, 30, and 40 from being output through sides of thelight emitting stacked structure, and thus, may include a material thatabsorbs or reflects light. The light-opaque layer may be formed bydepositing two insulating layers of different refractive indices. Forexample, the light-opaque layer may be formed by stacking a material ofa low refractive index and a material of a high refractive indexsequentially or by stacking insulating layers of different refractiveindices. Materials of different refractive indices are not specificallylimited, and may include, for example, SiO₂ and SiN_(x).

As described above, according to an exemplary embodiment, it is possibleto simultaneously form a wire part and a contact at a plurality ofepitaxial stacks after sequentially stacking the plurality of epitaxialstacks.

FIG. 35 is a schematic cross-sectional view of a light emitting stackedstructure according to an exemplary embodiment.

Referring to FIG. 35, a light emitting stacked structure according to anexemplary embodiment a plurality of epitaxial stacks, which aresequentially stacked. The epitaxial stacks are disposed a substrate 200,which has substantially a plate shape having a front surface and a backsurface.

A plurality of epitaxial stacks may be mounted on the front surface ofthe substrate 200, and the substrate 200 may be provided in variousforms. The substrate 200 may be formed of an insulating material. Thematerial of the substrate 200 may include glass, quartz, organicpolymer, organic/inorganic composite, etc. However, the inventiveconcepts are not limited to a particular material of the substrate 200.For example, the substrate 200 may include various materials as long asit has an insulating property. In an exemplary embodiment, a wire partwhich may provide a light emitting signal and a common voltage to eachepitaxial stack may be further disposed on the substrate 200. Inparticular, when each epitaxial stack is driven in an active matrixmanner, a driving element including a thin film transistor may befurther disposed on the substrate 200 in addition to the wire part. Assuch, the substrate 200 may be formed as a printed circuit substrate, ormay be implemented with a complex substrate, in which the wire partand/or the driving element are formed on the glass, silicon, quartz,organic polymer, or organic/inorganic composite.

The plurality of epitaxial stacks may be sequentially stacked on thefront surface of the substrate 200. Each of the plurality of epitaxialstacks emits a color light.

In an exemplary embodiment, two or more epitaxial stacks may be disposedover one another, and the epitaxial stacks may emit color lights havingdifferent wavelength bands, respectively. More particularly, a pluralityof epitaxial stacks may have different energy bands. Hereinafter, alight emitting stacked structure will be described as including threesequentially stacked epitaxial stack layers disposed on the substrate200, however, the inventive concepts are not limited to a particularnumber of stacked epitaxial layers.

Each epitaxial stack may emit a color light in a visible wavelength bandamong various wavelength bands. Light emitted from the lowermostepitaxial stack may have the longest wavelength, which has the lowestenergy band, and light emitted from epitaxial stacks disposed thereovermay emit light having a shorter wavelength. Light emitted from theuppermost epitaxial stack may have the shortest wavelength, which as thehighest energy band. For example, the first epitaxial stack 220 may emita first color light L1, a second epitaxial stack 230 may emit a secondcolor light L2, and a third epitaxial stack 240 may emit a third colorlight L3. The first to third color lights L1 to L3 may correspond tolight having different colors from each other, e.g., differentwavelength bands, and the wavelengths of the first to third color lightsL1 to L3 may become sequentially short. In particular, the first tothird color lights L1 to L3 may have different wavelength bands, and theenergy of light may increase from the first color light L1 toward thethird color light L3.

In the illustrated exemplary embodiment, the first color light L1 may bea red light, the second color light L2 may be a green light, and thethird color light L3 may be a blue light. However, the inventiveconcepts are not limited thereto. When the light emitting stackedstructure includes a micro LED, which has a surface area less than about10,000 square μm as known in the art, or less than about 4,000 square μmor 2,500 square μm in other exemplary embodiments, the first epitaxialstack 220 may emit any one of red, green, and blue light, and the secondand third epitaxial stacks 230 and 240 may emit a different one of red,green, and blue light, without adversely affecting operation, due to thesmall form factor of a micro LED.

Each of the epitaxial stacks 220, 230, and 240 emits light in an upwarddirection (hereinafter referred to as a “front direction”) from thesubstrate 200. In this case, light emitted from one epitaxial stacktravels in the front direction through any other epitaxial stack(s)located on a path of the light. The front direction may correspond to adirection in which the first, second, and third epitaxial stacks 220,230, and 240 are stacked.

Hereinafter, the front direction of the substrate 200 may also bereferred to as an “upper direction” and the back direction of thesubstrate 200 may also be referred to as a “lower direction”. However,the terms “upper direction” and the “lower direction” are relativeterms, and may vary with a direction in which epitaxial stacks of thelight emitting stacked structure is arranged or stacked.

Each of the epitaxial stacks 220, 230, and 240 emits light in the upperdirection, and each of the epitaxial stacks 220, 230, and 240 transmitsmost of light emitted from a lower epitaxial stack. In particular, lightemitted from the first epitaxial stack 220 passes through the secondepitaxial stack 230 and the third epitaxial stack 240 to travel in thefront direction, and light emitted from the second epitaxial stack 230passes through the third epitaxial stack 240 to travel in the frontdirection. As such, at least some or all of the remaining epitaxialstacks other than the lowermost epitaxial stack may be formed of alight-transmitting material. For example, the light-transmittingmaterial includes a material transmitting light of a particularwavelength or a portion of light of the particular wavelength, as wellas a material transmitting the whole light. In an exemplary embodiment,each of the epitaxial stacks 220, 230, and 240 may transmit 60% or moreof light emitted from an epitaxial stack disposed thereunder. In anotherexemplary embodiment, each of the epitaxial stacks 220, 230, and 240 maytransmit 80% or more of light emitted from an epitaxial stack disposedthereunder. In another exemplary embodiment, each of the epitaxialstacks 220, 230, and 240 may transmit 90% or more of light emitted froman epitaxial stack disposed thereunder.

The epitaxial stacks 220, 230, and 240 of the light emitting stackedstructure according to an exemplary embodiment may be independentlydriven by connecting signal lines applying light emitting signals to theepitaxial stacks, respectively. Also, the light emitting stackedstructure according to an exemplary embodiment may implement variouscolors depending on whether light is emitted from the epitaxial stacks220, 230, and 240. Since epitaxial stacks emitting light of differentwavelengths are vertically formed to overlap each other, it is possibleto form the light emitting stacked structure.

FIGS. 36A and 36B are cross-sectional views of a light emitting stackedstructure according to exemplary embodiments.

Referring to FIG. 36A, in the light emitting stacked structure accordingto an exemplary embodiment, the first epitaxial stack 220 may bedisposed on the substrate 200 with a first adhesive layer 60 ainterposed therebetween. The first adhesive layer 260 a may be formed ofa conductive or non-conductive material. When the first adhesive layer260 a needs to be electrically connected to the substrate 200, a partialregion of the first adhesive layer 260 a may have a conductivity. Thefirst adhesive layer 260 a may be formed of a transparent or opaquematerial. In an exemplary embodiment, when the substrate 200 is formedof an opaque material and a wire part and the like are formed on thesubstrate 200, the first adhesive layer 260 a may be formed of an opaquematerial, for example, that absorbs light. Various polymer adhesives,for example, an epoxy-based polymer adhesive may be used as a lightabsorption material for the first adhesive layer 260 a.

The second and third epitaxial stacks 230 and 240 may be disposed on thefirst epitaxial stack 220 with a second adhesive layer 260 b interposedtherebetween. The second adhesive layer 260 b is formed of anon-conductive material and may include a light-transmitting material.For example, an optically clear adhesive may be used as the secondadhesive layer 260 b. The material forming the second adhesive layer 260b is not particularly limited as long as an adhesive layer may beoptically clear and may be stably adhered to each epitaxial stack. Forexample, the second adhesive layer 260 b may include epoxy polymer,various photoresists, parylene, PMMA (Poly(methyl methacrylate)), BCB(benzocyclobutene), etc., such as SU-8, as an organic material, and mayinclude silicon oxide, aluminum oxide, melting glass, etc., as aninorganic material. In some exemplary embodiments, conductive oxide maybe used as an adhesive layer. In this case, the conductive oxide shouldbe insulated from any other element. When an organic material is used asan adhesive layer, and when molten glass of the inorganic materials isused, the material may be coated on an adhesive surface and may bebonded thereon at a high temperature and a high pressure in a vacuumstate. When an inorganic material (except for molten glass) is used asan adhesive layer, the inorganic material may be bonded on an adhesivelayer through the following processes: depositing of the inorganicmaterial on the adhesive layer, chemical-mechanical planarization (CMP),plasma processing on a surface of a resultant structure, and bonding athigh vacuum.

The first epitaxial stack 220 includes a p-type semiconductor layer 225,an active layer 223, and an n-type semiconductor layer 221. The secondepitaxial stack 230 includes a p-type semiconductor layer 235, an activelayer 233, and an n-type semiconductor layer 231, and the thirdepitaxial stack 240 includes a p-type semiconductor layer 245, an activelayer 243, and an n-type semiconductor layer 241.

The first epitaxial stack 220 may include the p-type semiconductor layer225, the active layer 223, and the n-type semiconductor layer 221sequentially stacked on the substrate 200, and may include asemiconductor material emitting a red light, for example.

The semiconductor material emitting a red light may include aluminumgallium arsenide (AlGaAs), gallium arsenide phosphide (GaAsP), aluminumgallium indium phosphide (AlGaInP), gallium phosphide (GaP), etc.However, the semiconductor material emitting a red light is not limitedthereto, and various other materials may be used.

A first p-type contact electrode 225 p may be provided under the p-typesemiconductor layer 225 of the first epitaxial stack 220. The firstp-type contact electrode 225 p of the first epitaxial stack 220 may beformed of a single-layered or multi-layered metal. For example, variousmaterials including metals, such as Al, Ti, Cr, Ni, Au, Ag, Ti, Sn, Ni,Cr, W, and Cu, or an alloy thereof may be used as the first p-typecontact electrode 225 p. The first p-type contact electrode 225 p mayinclude a metal having high reflectivity. As the first p-type contactelectrode 225 p is formed of a metal of high reflectivity, the lightemission efficiency from the first epitaxial stack 220 in the upperdirection may be improved.

The second epitaxial stack 230 includes the n-type semiconductor layer231, the active layer 233, and the p-type semiconductor layer 235sequentially stacked one over another. The n-type semiconductor layer231, the active layer 233, and the p-type semiconductor layer 235 mayinclude a semiconductor material emitting a green light, for example.The semiconductor material emitting a green light may include indiumgallium nitride (InGaN), gallium nitride (GaN), allium phosphide (GaP),AlGaInP, AlGaP, etc. However, the semiconductor material emitting agreen light is not limited thereto, and various other materials may beused.

A second n-type contact electrode 231 n is provided under the n-typesemiconductor layer 231 of the second epitaxial stack 230. The secondn-type contact electrode 231 n is interposed between the first epitaxialstack 220 and the second epitaxial stack 230, in detail, between thesecond adhesive layer 260 b and the second epitaxial stack 230.

The second n-type contact electrodes 231 n may be formed of transparentconductive oxide (TCO). The transparent conductive oxide may include tinoxide (SnO), indium oxide (InO2), zinc oxide (ZnO), indium tin oxide(ITO), indium tin zinc oxide (ITZO), etc. A transparent conductivecompound may be deposited through chemical vapor deposition (CVD) andphysical vapor deposition (PVD) using an evaporator and a sputter. Thesecond n-type contact electrodes 231 n may have a thickness enough tofunction as an etch stopper in a fabricating process to be describedlater, while satisfying a predetermined light transmittance, forexample, a thickness of approximately 2000 angstroms or approximately 2micrometers.

A second p-type contact electrode 235 p is provided under the p-typesemiconductor layer 235 of the second epitaxial stack 230. The secondp-type contact electrode 235 p is interposed between the secondepitaxial stack 230 and the third epitaxial stack 240.

The third epitaxial stack 240 includes the p-type semiconductor layer245, the active layer 243, and the n-type semiconductor layer 241sequentially stacked one over another. The p-type semiconductor layer245, the active layer 243, and the n-type semiconductor layer 241 mayinclude a semiconductor material emitting a blue light, for example. Thesemiconductor material emitting a blue light may include GaN, InGaN,ZnSe, etc. However, the semiconductor material emitting a blue light isnot limited thereto, and various other materials may be used.

A third p-type contact electrode 245 p is provided under the p-typesemiconductor layer 245 of the third epitaxial stack 240. The thirdp-type contact electrode 245 p is interposed between the secondepitaxial stack 230 and the third epitaxial stack 240.

The second p-type contact electrode 235 p and the third p-type contactelectrode 245 p between the p-type semiconductor layer 235 of the secondepitaxial stack 230 and the p-type semiconductor layer 245 of the thirdepitaxial stack 240 may form a shared electrode, which may be shared bythe second epitaxial stack 230 and the third epitaxial stack 240.

The second p-type contact electrode 235 p and the third p-type contactelectrode 245 p may at least partially contact each other, and may bephysically and/or electrically connected. In this manner, even though asignal is applied to at least one of the second p-type contact electrode235 p and the third p-type contact electrode 245 p, the same signal maybe applied to the p-type semiconductor layer 235 of the second epitaxialstack 230 and the p-type semiconductor layer 245 of the third epitaxialstack 240. For example, when a common voltage is applied to one side ofany one of the second p-type contact electrode 235 p and the thirdp-type contact electrode 245 p, the common voltage is applied to thep-type semiconductor layer of each of the second and third p-typeepitaxial stacks 230 and 240 through both second p-type contactelectrode 235 p and the third p-type contact electrode 245 p.

In the illustrated exemplary embodiment, each of the n-typesemiconductor layers 221, 231, and 241 and the p-type semiconductorlayers 225, 235, and 245 of the first, second, and third epitaxialstacks 220, 230, and 240 is illustrated as a single layer, but in someexemplary embodiments, each layer may be a multi-layer or may include asupperlattic layer. Also, the active layers 223, 233, and 243 of thefirst, second, and third epitaxial stacks 220, 230, and 240 may includea single quantum well structure or a multiple quantum well structure.

In the illustrated exemplary embodiment, the second and third p-typecontact electrodes 235 p and 245 p, which constitute a shared electrode,substantially cover the second and third epitaxial stacks 230 and 240.The second and third p-type contact electrodes 235 p and 245 p may beformed of a transparent conductive material, which may transmit lightemitted from a lower epitaxial stack. For example, each of the secondand third p-type contact electrodes 235 p and 245 p may be formed oftransparent conductive oxide (TCO). The transparent conductive oxide mayinclude tin oxide (SnO), indium oxide (InO₂), zinc oxide (ZnO), indiumtin oxide (ITO), indium tin zinc oxide (ITZO), etc. A transparentconductive compound may be deposited through chemical vapor deposition(CVD) and physical vapor deposition (PVD) using an evaporator and asputter. The second and third p-type contact electrodes 235 p and 245 pmay have a thickness enough to function as an etch stopper in afabricating process to be described later, while satisfying apredetermined light transmittance, for example, a thickness ofapproximately 2000 angstroms or approximately 2 micrometers.

A common line may be connected to the first, second, and third p-typecontact electrodes 225 p, 235 p, and 245 p. The common line may applythe common voltage. Also, light emitting signal lines may berespectively connected to the n-type semiconductor layers 221, 231, and241 of the first, second, and third epitaxial stacks 220, 230, and 240.In an exemplary embodiment, a common voltage SC is applied to the firstp-type contact electrode 225 p, the second p-type contact electrode 235p, and the third p-type contact electrode 245 p through the common line,and the light emission of the first, second, and third epitaxial stacks220, 230, and 240 are controlled by applying light emitting signals tothe n-type semiconductor layer 221 of the first epitaxial stack 220, thesecond n-type contact electrode 231 n of the second epitaxial stack 230,and the n-type semiconductor layer 241 of the third epitaxial stack 240through the light emitting signal lines, respectively. The lightemitting signals may include first, second, and third light emittingsignals SR, SG, and SB respectively corresponding to the first, second,and third epitaxial stacks 220, 230, and 240. In an exemplaryembodiment, the first light emitting signal SR may be a signal foremitting a red light, the second light emitting signal SG may be asignal for emitting a green light, and the third light emitting signalSB may be a signal for emitting a blue light.

As described above, according to an exemplary embodiment, the samesignal may be simultaneously provided to two adjacent epitaxial stacksthrough the shared electrode. In this case, semiconductor layers of thetwo adjacent epitaxial stacks facing each other may be doped withimpurities of the same polarity type. For example, the two semiconductorlayers facing each other with a shared electrode interposed therebetweenmay be a p-type semiconductor layer.

FIG. 36A shows three epitaxial stacks and the shared electrode providedbetween the second and third epitaxial stacks 230 and 240, but theinventive concepts are not limited thereto. For example, a location ofthe shared electrode may be variously changed as long as two epitaxialstacks are adjacent to each other. For example, when applying the samesignal to two semiconductor layers in a light emitting stacked structureincluding four epitaxial stacks, the shared electrode may be provided atany other location between two semiconductor layers that face each otherand are doped with impurities of the same polarity type.

According to an exemplary embodiment, since the same signal may beapplied to two adjacent epitaxial stacks through the shared electrode,the number of contact parts for applying signals to the respectiveepitaxial stacks may be reduced. For example, a contact part may beformed for each of three epitaxial stacks to apply a common voltage tothe three epitaxial stacks. However, according to an exemplaryembodiment, the common voltage may be applied to three epitaxial stacksonly through two contact parts. A detailed contact structure will bedescribed in more detail below.

FIG. 36B is a cross-sectional view of a light emitting stacked structureaccording to another exemplary embodiment. The light emitting stackedstructure according to the illustrated exemplary embodiment issubstantially similar to that of FIG. 36A, except that the commonvoltage is applied to the n-type semiconductor layers 221, 231, and 241of the first, second, and third epitaxial stacks 220, 230, and 240, andlight emitting signals are applied to the p-type semiconductor layers225, 235, and 245 of the first, second, and third epitaxial stacks 220,230, and 240.

Referring to FIG. 36B, the first epitaxial stack 220 may include then-type semiconductor layer 221, the active layer 223, and the p-typesemiconductor layer 225 sequentially stacked on the substrate 200, andmay include a semiconductor material emitting a red light.

A first n-type contact electrode 221 n may be provided under the n-typesemiconductor layer 221 of the first epitaxial stack 220. The firstn-type contact electrode 221 n of the first epitaxial stack 220 may be asingle-layered or multi-layered metal. In an exemplary embodiment, thefirst n-type contact electrode 221 n may be formed of an Au alloy, suchas AuGe or AuTe.

The second epitaxial stack 230 includes the p-type semiconductor layer235, the active layer 2233, and the n-type semiconductor layer 231sequentially stacked one over another. The p-type semiconductor layer235, the active layer 233, and the n-type semiconductor layer 231 mayinclude a semiconductor material emitting a green light.

A second p-type contact electrode 235 p is provided under the p-typesemiconductor layer 235 of the second epitaxial stack 230. The secondp-type contact electrode 235 p is interposed between the first epitaxialstack 220 and the second epitaxial stack 230, in detail, between thesecond adhesive layer 260 b and the second epitaxial stack 230.

A second n-type contact electrode 231 n is provided on the n-typesemiconductor layer 231 of the second epitaxial stack 230. The secondp-type contact electrode 231 n is interposed between the secondepitaxial stack 230 and the third epitaxial stack 240.

The third epitaxial stack 240 includes the n-type semiconductor layer241, the active layer 243, and the p-type semiconductor layer 245sequentially stacked one over another. The n-type semiconductor layer241, the active layer 243, and the p-type semiconductor layer 245 mayinclude a semiconductor material emitting a blue light.

A third n-type contact electrode 241 n is provided under the n-typesemiconductor layer 241 of the third epitaxial stack 240. The thirdn-type contact electrode 241 n is interposed between the secondepitaxial stack 230 and the third epitaxial stack 240.

The second n-type contact electrode 231 n and the third n-type contactelectrode 241 n between the n-type semiconductor layer 231 of the secondepitaxial stack 230 and the n-type semiconductor layer 241 of the thirdepitaxial stack 240 may constitute a shared electrode, which may beshared by the second epitaxial stack 230 and the third epitaxial stack240.

The second n-type contact electrode 231 n and the third n-type contactelectrode 241 n may at least partially contact each other, and may bephysically and/or electrically connected to each other. In this manner,even though a signal is applied to at least one of the second n-typecontact electrode 231 n and the third n-type contact electrode 241 n,the same signal may be applied to the n-type semiconductor layer 231 ofthe second epitaxial stack 230 and the n-type semiconductor layer 241 ofthe third epitaxial stack 240.

In the illustrated exemplary embodiment, a common line may be connectedto the first, second, and third n-type contact electrodes 221 n, 231 n,and 241 n. Light emitting signal lines may be respectively connected tothe p-type semiconductor layers 225, 235, and 245 of the first, second,and third epitaxial stacks 220, 230, and 240. The common voltage SC isapplied to the first n-type contact electrode 221 n, the second n-typecontact electrode 231 n, and the third n-type contact electrode 241 nthrough the common line, and the light emission of the first, second,and third epitaxial stacks 220, 230, and 240 are controlled by applyinglight emitting signals to the p-type semiconductor layer 225 of thefirst epitaxial stack 220, the second p-type contact electrode 235 p ofthe second epitaxial stack 230, and the p-type semiconductor layer 245of the third epitaxial stack 240 through the light emitting signallines, respectively.

According to the exemplary embodiments, the first, second, and thirdepitaxial stacks 220, 230, and 240 are driven in response to relevantlight emitting signals, respectively. More particularly, the firstepitaxial stack 220 is driven by the first light emitting signal SR, thesecond epitaxial stack 230 is driven by the second light emitting signalSG, and the third epitaxial stack 240 is driven by the third lightemitting signal SB. The first, second, and third light emitting signalsSR, SG, and SB may be independently applied to the first, second, andthird epitaxial stacks 220, 230, and 240, and thus, the first, second,and third epitaxial stacks 220, 230, and 240 may be driven independentlyof each other. As such, the light emitting stacked structure maygenerate light of a color, which may be variously determined by acombination of the first, second, and third color lights emitted fromthe first, second, and third epitaxial stacks 220, 230, and 240 in theupper direction.

When displaying a color, different color lights are not emitted fromdifferent planes, but different color lights are emitted from anoverlapping region, and thus, the light emitting stacked structureaccording to an exemplary embodiment is capable of integrating a lightemitting element with reduced size. In general, conventional lightemitting elements emitting different color lights, for example, red,green, and blue lights, are spaced apart from each other on the sameplane to implement a full color. In this case, as each light emittingelement is disposed on the same plane, the element occupy a relativelylarge area. However, light emitting elements according to exemplaryembodiments include a stacked structure, in which the elements overlapeach other in one area to emit different color lights, and thus, a fullcolor may be implemented in a significantly less area. As such, ahigh-resolution device may be fabricated in a small area.

In addition, even if a conventional light emitting device was fabricatedin a stack manner, the conventional light emitting device may bemanufactured by forming an individual contact part for a connection withthe individual light emitting element through a line for each lightemitting element, which would increase manufacturing complexities due toa complicated structure. However, the light emitting stacked structureaccording to an exemplary embodiment may be formed by forming a multipleepitaxial stack structure on one substrate, forming a contact part atthe multiple epitaxial stack structure through a minimum process, andconnecting the contact part and the multiple epitaxial stack structure.In particular, since the number of contact points is reduced with theusage of a shared electrode, a structure and the fabricating methodthereof may be further simplified. Also, as compared to a conventionaldisplay device fabricating method in which a light emitting element ofan individual color is fabricated and is individually mounted, accordingto the inventive concepts, only one light emitting stacked structure ismounted, instead of a plurality of light emitting elements, therebysignificantly simplifying a fabricating method.

The light emitting stacked structure according to an exemplaryembodiment may further include various elements to provide a high-purityand high-efficiency color light. For example, the light emitting stackedstructure according to an exemplary embodiment may include a wavelengthpass filter for blocking light of a relatively short wavelength fromtraveling toward an epitaxial stack that emits light with a longerwavelength.

Hereinafter, descriptions of a light emitting stacked structureaccording to exemplary embodiments will be focused on a difference fromthat of FIGS. 36A and 36B. As such, detailed descriptions as to thesubstantially the same elements will be omitted to avoid redundancy.

FIG. 37 is a schematic cross-sectional view of a light emitting stackedstructure according to an exemplary embodiment.

Referring to FIG. 37, a light emitting stacked structure according to anexemplary embodiment may include a first wavelength pass filter 271between the first epitaxial stack 220 and the second epitaxial stack230.

The first wavelength pass filter 271 may transmit a first color lightemitted from the first epitaxial stack 220, and may block or reflect anyother lights except for the first color light. As such, the first colorlight emitted from the first epitaxial stack 220 may travel in the upperdirection, but second and third color lights emitted from the second andthird epitaxial stacks 230 and 240 may not travel toward the firstepitaxial stack 220, and may be reflected or blocked by the firstwavelength pass filter 271.

When the second and third color light, which has a higher energy and ashorter wavelength than the first color light are incident onto thefirst epitaxial stack 220, the second and third color light may induceadditional light emission in the first epitaxial stack 220. In theillustrated exemplary embodiment, the second and third color light isprevented from being incident onto the first epitaxial stack 220 by thefirst wavelength pass filter 271.

In an exemplary embodiment, a second wavelength pass filter 273 may bedisposed between the second epitaxial stack 230 and the third epitaxialstack 240. In particular, the second wavelength pass filter 273 may beprovided between the second p-type contact electrode 235 p and the thirdp-type contact electrode 245 p, together which constitute a sharedelectrode. The second wavelength pass filter 273 may be formed to besmaller than the second p-type contact electrode 235 p and the thirdp-type contact electrode 245 p, such that the second p-type contactelectrode 235 p and the third p-type contact electrode 245 p areconnected to each other in a region where the second wavelength passfilter 273 is not formed. For example, the second wavelength pass filter273 may include at least one contact hole, and the second p-type contactelectrode 235 p and the third p-type contact electrode 245 p may beconnected to each other through the contact hole.

The second wavelength pass filter 273 may transmit the first and secondcolor light emitted from the first and second epitaxial stacks 220 and230, and may reflect or block any other light except for the first andsecond color light. As such, the first and second color light emittedfrom the first and second epitaxial stacks 220 and 230 may travel in theupper direction, but the third color light emitted from the thirdepitaxial stack 240 may not travel toward the first and second epitaxialstacks 220 and 230, and may be reflected or blocked by the secondwavelength pass filter 273.

When the third color light, which has a higher energy and a shorterwavelength than the first and second color light is incident onto thefirst and second epitaxial stacks 220 and 230, the third color light mayinduce additional light emission in the first and second epitaxialstacks 220 and 230. In the illustrated exemplary embodiment, the thirdcolor light is prevented from being incident onto the first and secondepitaxial stacks 220 and 230 by the second wavelength pass filter 273.

The light emitting stacked structure according to an exemplaryembodiment may further include various elements to provide a uniformlight. For example, the light emitting stacked structure according to anexemplary embodiment may have various concavo-convex portions on a lightoutput surface.

FIGS. 38 and 39 are cross-sectional views of a light emitting stackedstructure according to exemplary embodiments.

Referring to FIGS. 38 and 39, the light emitting stacked structureaccording to exemplary embodiments may include a concavo-convex portionformed on an upper surface of at least one of the first, second, andthird epitaxial stacks 220, 230, and 240.

The concavo-convex portion PR may be selectively formed on the first,second, and third epitaxial stacks 220, 230, and 240. For example, asillustrated in FIG. 38, the concavo-convex portions PR may berespectively provided on the first and third epitaxial stacks 220 and240. According to another exemplary embodiment, the concavo-convexportions PR may be provided on the first and third epitaxial stacks 220and 240, as shown in FIG. 39. The concavo-convex portion PR may beprovided on a semiconductor layer corresponding to a light outputsurface of the epitaxial stack.

According to an exemplary embodiment, when the concavo-convex portion PRis formed on the first epitaxial stack 220, the first wavelength passfilter 271 may be provided directly on an upper surface thereof. In someexemplary embodiments, an additional insulating layer may be providedbetween the first epitaxial stack 220 and the first wavelength passfilter 271. An insulating layer provided between the first epitaxialstack 220 and a second wavelength pass filter 273 may be an insulatinglayer that planarizes a surface thereof, such that the second wavelengthpass filter 273 may function efficiently on the first epitaxial stack220.

The concavo-convex portion PR may improve light emission efficiency andmay be formed in various shapes, such as a many-sided pyramid, ahemisphere, and rough surfaces arranged randomly. The concavo-convexportion PR may be formed by using a sapphire substrate textured orpatterned through various etching processes.

In an exemplary embodiment, the first, second, and third color lightemitted from the first, second, and third epitaxial stacks 220, 230, and240 may have different light intensities, which may cause a differencein visibility. According to an exemplary embodiment, the light emissionefficiency may be improved by selectively forming the concavo-convexportion PR on light output surfaces of the first, second, and thirdepitaxial stacks 220, 230, and 240, thus reducing the difference invisibility of the first to third color light. For example, a red colorand/or a blue color may have lower visibility than a green color. Assuch, the difference in visibility may be reduced by texturing of thefirst epitaxial stack 220 and/or the third epitaxial stack 240. Forexample, when an epitaxial stack emitting a red light is disposed on thelowermost of the light emitting stacked structure, the intensity of thered light may be small. As such, the light efficiency may be improved byforming the concavo-convex portion PR on an upper surface of theepitaxial stack emitting red light.

The light emitting stacked structure according to an exemplaryembodiment may express various colors, and thus, may be adopted as apixel, which will be described in more detail below.

FIG. 40 is a plan view of a display device according to an exemplaryembodiment, and FIG. 41 is an enlarged view of portion P1 of FIG. 41.

Referring to FIGS. 40 and 41, a display device 200 according to anexemplary embodiment may display any visual information, for example, atext, a video, a photo, a two-dimensional or three-dimensional image,etc.

The display device 200 may be provided in various shapes, such as apolygon including straight line segments with closed loop to form aclosed polygonal chain or circuit, a circular, an elliptical, etc.including a curved side; and a semicircular, a semi-elliptical, etc.including a straight or curved side. Hereinafter, the display device 200will be described as having substantially a rectangular shape, but theinventive concepts are not limited thereto.

The display device 200 includes a plurality of pixels 2110 displaying animage. Each of the pixels 2110 may correspond to a minimum unitdisplaying an image. Each pixel 2110 may include the light emittingstacked structure according to exemplary embodiments illustrated withreference to FIGS. 35 to 39, and may emit a white light and/or a colorlight.

In an exemplary embodiment, each pixel 2110 includes a first subpixel2110R emitting a red light, a second subpixel 2110G emitting a greenlight, and a third subpixel 2110B emitting a blue light. The first,second, and third subpixels 2110R, 2110G, and 2110B may correspond tothe first, second, and third epitaxial stacks 220, 230, and 240 of theabove-described light emitting stacked structure, respectively.

The pixels 2110 are arranged in the matrix of rows and columns. As usedherein, the pixels 2110 being arranged in the matrix of rows and columnsmay refer to the pixels 2110 being arranged exactly in line along a rowor a column, or substantially arranged along a row or a column in azigzag shape whereby the locations of the pixels 2110 may be changed,etc.

FIG. 42 is a block diagram of a display device according to an exemplaryembodiment.

Referring to FIG. 42, the display device 200 according to an exemplaryembodiment includes a timing controller 2350, a scan driver unit 2310, adata driver unit 2330, a wire part, and pixels. When each pixel includesa plurality of subpixels, each subpixel may be connected to the scandriver unit 2310, the data driver unit 2330, etc., through the wirepart.

The timing controller 2350 receives various control signals and imagedata from the outside (e.g., an external system which transmits imagedata) to drive the display device 200. The timing controller 2350 mayrearrange the received image data and provide the rearranged data to thedata driver unit 2330. The timing controller 2350 may generate scancontrol signals and data control signals to drive the scan driver unit2310 and the data driver unit 2330, and provide the generated scancontrol signals and the generated data control signals to the scandriver unit 2310 and the data driver unit 2330.

The scan driver unit 2310 may generate a scan signal corresponding tothe scan control signal provided from the timing controller 2350.

The data driver unit 2330 may generate a data signal corresponding tothe data control signal and the image data provided from the timingcontroller 2350.

The wire part includes a plurality of signal lines. In particular, thewire part includes scan lines 2130 connecting the scan driver unit 2310and the subpixels, and data lines 2120 connecting the data driver unit2330 and the subpixels. The scan lines 2130 may be connected to thesubpixels of each pixel 2110. The scan lines include first, second, andthird scan lines 2130R, 2130G, and 2130B, and hereinafter, may becollectively indicated with reference numeral “130”.

The wire part may connect the timing controller 2350 and the scan driverunit 2310, the timing controller 2350 and the data driver unit 2330, orany other components, and may further includes a plurality of lines fortransferring relevant signals.

The scan lines 2130 provide scan signals generated by the scan driverunit 2310 to the subpixels. Data signals generated by the data driverunit 2330 are output to the data lines 2120.

The subpixels are connected to the scan lines 2130 and the data lines2120. The subpixels selectively emit light in response to data signalsreceived from the data lines 2120 when scan signals are supplied fromthe scan lines 2130. For example, during each frame period, eachsubpixel emits light with luminance corresponding to the received datasignal. A subpixel supplied with a data signal corresponding to blackluminance may not emit light during a relevant frame period, thusdisplaying a black color.

In an exemplary embodiment, the subpixels may be driven in a passivedriving manner or an active driving manner. When the display device 200is driven in the active driving manner, the display device 200 may bedriven based on first and second pixel voltages additionally suppliedthereto, in addition to a scan signal and a data signal.

FIG. 43 is a circuit diagram illustrating one subpixel according to anexemplary embodiment. In particular, the circuit diagram according tothe illustrated exemplary embodiment may correspond to a subpixel, suchas a red subpixel 2110R included in a passive-type display device. Thesecond and third subpixels 2110G and 2110B may be driven insubstantially the same manner as the first subpixel 2110R, and thus,repeated descriptions as to the second and third subpixels 2110G and2110B will be omitted to avoid redundancy.

Referring to FIG. 43, the first subpixel 2110R includes a light emittingelement 2150 connected between the scan line 2130 and the data line2120. The light emitting element 2150 may correspond to the firstepitaxial stack 220. When a voltage of a threshold voltage or higher isapplied between a p-type semiconductor layer and an n-type semiconductorlayer, the first epitaxial stack 220 emits light with luminancecorresponding to a magnitude of the applied voltage. In particular, thelight emission of the first subpixel 2110R may be controlled byadjusting a voltage of a scan signal applied to the scan line 2130and/or a voltage of a data signal applied to the data line 2120.

FIG. 44 is a circuit diagram illustrating a first subpixel according toan exemplary embodiment. The circuit diagram according to theillustrated exemplary embodiment may correspond to a subpixel includedin an active-type display device.

When the display device 200 is an active-type display device, the firstsubpixel 2110R may be further supplied with first and second pixelvoltages ELVDD and ELVSS, as well as a scan signal and a data signal.

Referring to FIG. 44, the first subpixel 2110R include the lightemitting element 2150 and a transistor unit connected to the lightemitting element 2150.

The light emitting element 2150 may correspond to the first epitaxialstack 220. An n-type semiconductor layer of the light emitting element2150 may be connected to the first pixel voltage ELVDD through thetransistor unit, and a p-type semiconductor layer thereof may beconnected to the second pixel voltage ELVSS. The first pixel voltageELVDD and the second pixel voltage ELVSS may have different potentials.For example, a potential of the second pixel voltage ELVSS may be lowerthan a potential of the first pixel voltage ELVDD by not smaller than athreshold voltage of the light emitting element 2150. The light emittingelement 2150 may emit light with luminance corresponding to a drivingcurrent controlled by the transistor unit.

According to an exemplary embodiment, the transistor unit includes firstand second transistors M1 and M2 and a storage capacitor Cst. However, astructure of the transistor unit may be variously modified and is notlimited to that shown in FIG. 44.

A source electrode of the first transistor M1 (a switching transistor)is connected to the data line 2120, and a drain electrode thereof isconnected to a first node N1. A gate electrode of the first transistorM1 is connected to the first scan line 2130R. When a scan signal of avoltage enough to turn on the first transistor M1 is supplied from thefirst scan line 2130R, the first transistor M1 is turned on, thusconnecting the data line 2120 and the first node N1. In this case, adata signal of a relevant frame is supplied to the data line 2120, andthus, the data signal is transferred to the first node N1. The datasignal transferred to the first node N1 is charged in the storagecapacitor Cst.

A source electrode of the second transistor M2 (a driving transistor) isconnected to the first pixel voltage ELVDD, and a drain electrodethereof is connected to an n-type semiconductor layer. A gate electrodeof the second transistor M2 is connected to the first node N1. Thesecond transistor M2 controls the amount of driving current, which issupplied to the light emitting element 2150, based on a voltage of thefirst node N1.

A first end of the storage capacitor Cst is connected to the first pixelvoltage ELVDD, and a second end thereof is connected to the first nodeN1. The storage capacitor Cst charges a voltage corresponding to a datasignal supplied to the first node N1, and maintains the charged voltageuntil a data signal of a next frame is supplied.

Although FIG. 44 shows the transistor unit including two transistors,however, the inventive concepts are not limited thereto. For example,the transistor unit may include more transistors, more capacitors, etc.Since, the structure of first and second transistors, the storagecapacitor, and the signal lines are well known in the art, and thus,detailed descriptions thereof will be omitted.

Hereinafter, the pixel will be described with reference to a passivematrix type, however, the inventive concepts are not limited thereto.

FIG. 45 is a plan view of a pixel according to an exemplary embodiment,and FIG. 46 is a cross-sectional view taken along line I-I′ of FIG. 45.

Referring to FIGS. 45 and 46, a pixel according to an exemplaryembodiment includes a light emitting region in which a plurality ofepitaxial stacks are stacked, and a peripheral region surrounding thelight emitting region. In the illustrated exemplary embodiment, theplurality of epitaxial stacks include the first, second, and thirdepitaxial stacks 220, 230, and 240.

The pixel according to an exemplary embodiment has the light emittingregion in which a plurality of epitaxial stacks are stacked in a planview. A contact part for connecting a wire part to the first, second,and third epitaxial stacks 220, 230, and 240 is provided on at least sone side of the light emitting region. The contact part includes acommon contact part 250 c for applying a common voltage to the first,second, and third epitaxial stacks 220, 230, and 240, a first contactpart 220 c for providing a light emitting signal to the first epitaxialstack 220, a second contact part 230 c for providing a light emittingsignal to the second epitaxial stack 230, and a third contact part 240 cfor providing a light emitting signal to the third epitaxial stack 240.

In an exemplary embodiment, as illustrated in FIGS. 36A and 36B, astacked structure may be changed depending on the polarity type of asemiconductor layer of the first, second, and third epitaxial stacks220, 230, and 240 to which a common voltage is applied. In particular,in the common contact part 250 c, a contact electrode for applying thecommon voltage is provided for each of the first, second, and thirdepitaxial stacks 220, 230, and 240, and the contact electrodescorresponding to the first, second, and third epitaxial stacks 220, 230,and 240 may be referred to as “first, second, and third common contactelectrodes.” When the common voltage is applied to a p-typesemiconductor layer, the first, second, and third common contactelectrodes according to an exemplary embodiment may be the first,second, and third p-type common contact electrodes, respectively. Whenthe common voltage is applied to an n-type semiconductor layer, thefirst, second, and third common contact electrodes according to anotherexemplary embodiment may be first, second, and third n-type contactelectrodes, respectively. Hereinafter, the common voltage will bedescribed as being applied a p-type semiconductor layer, in particular,the first, second, and third common contact electrodes may be the first,second, and third p-type contact electrodes, respectively.

According to an exemplary embodiment, when the light emitting stackedstructure has substantially a quadrangular shape in a plan view, thecontact parts 220 c, 230 c, 240 c, and 250 c may be disposed in regionscorresponding to respective corners of the substantially quadrangularshape. However, the inventive concepts are not limited thereto, and thelocations of the contact parts 220 c, 230 c, 240 c, and 250 c may bevariously changed according to a shape of the light emitting stackedstructure.

The plurality of epitaxial stacks include the first, second, and thirdepitaxial stacks 220, 230, and 240. First, second, and third lightemitting signal lines providing light emitting signals to the first,second, and third epitaxial stacks 220, 230, and 240, respectively, anda common line providing a common voltage to the first, second, and thirdepitaxial stacks 220, 230, and 240 are connected to the first, second,and third epitaxial stacks 220, 230, and 240. In the illustratedexemplary embodiment, the first, second, and third light emitting signallines may correspond to the first, second, and third scan lines 2130R,2130G, and 2130B, respectively, and the common line may correspond tothe data line 2120. The first, second, and third scan lines 2130R,2130G, and 2130B and the data line 2120 are connected to the first,second, and third epitaxial stacks 220, 230, and 240.

In an exemplary embodiment, the first, second, and third scan lines2130R, 2130G, and 2130B may extend in a first direction (e.g., ahorizontal direction). The data line 2120 may extend in a seconddirection (e.g., a vertical direction) substantially crossing the first,second, and third scan lines 2130R, 2130G, and 2130B. However, theextending directions of the first, second, and third scan lines 2130R,2130G, and 2130B and the data line 2120 are not limited thereto, and maybe variously changed according to the arrangement of pixels.

As the data line 2120 and the first p-type contact electrode 225 p areelongated substantially in the second direction crossing the firstdirection and provide the common voltage to a p-type semiconductor layerof the first epitaxial stack 220, the data line 2120 and the firstp-type contact electrode 225 p may be considered as substantially thesame element. As such, the terms “first p-type contact electrode 225 p”and “data line 2120” will hereinafter be used interchangeably.

An ohmic electrode 225 p′ for an ohmic contact of the first p-typecontact electrode 225 p and the first epitaxial stack 220 is disposed ina light emitting region where the first p-type contact electrode 225 pis provided. The ohmic electrode 225 p′ may include a plurality of ohmicelectrodes. The ohmic electrode 225 p′ may be used for an ohmic contact,and may be formed of various materials. In an exemplary embodiment, theohmic electrode 225 p′ corresponding to a p-type ohmic electrode mayinclude Au(Zn) or Au(Be). Since reflectance of a material for the ohmicelectrode 225 p′ is lower than that of a material, such as Ag, Al, orAu, an additional reflection electrode may be further disposed. Forexample, Ag, Au, etc. may be used as a material for an additionalreflection electrode, and a metallic adhesive layer formed of amaterial, such as Ti, Ni, Cr, or Ta, may be disposed for adhesion withan adjacent element. In this case, the adhesive layer may be thinlydeposited on an upper surface and a lower surface of the reflectionelectrode including Ag, Au, etc.

The first scan line 2130R is connected to the first epitaxial stack 220through a first contact hole CH1, and the data line 2120 is connected tothe first epitaxial stack 220 through the ohmic electrode 225 p′. Thesecond scan line 2130G is connected to the second epitaxial stack 230through a second contact hole CH2, and the data line 2120 is connectedto the second epitaxial stack 230 through fourth and fifth contact holesCH4 and CH5. The third scan line 2130B is connected to the thirdepitaxial stack 240 through a third contact hole CH3, and the data line2120 is connected to the third epitaxial stack 240 through the fourthand fifth contact holes CH4 and CH5. The second and third epitaxialstacks 230 and 240 are simultaneously connected through a bridge line2120 b provided on the fourth and fifth contact holes CH4 and CH5.

An adhesive layer, a contact electrode, and a wavelength pass filter areprovided between the substrate 200, the first epitaxial stack 220, thesecond epitaxial stack 230, and the fourth epitaxial stack 240.Hereinafter, a pixel according to an exemplary embodiment will bedescribed in a stacked order.

According to the illustrated exemplary embodiment, the first epitaxialstack 220 is provided on the substrate 200, with the first adhesivelayer 260 a interposed therebetween. The first epitaxial stack 220 mayinclude a p-type semiconductor layer, an active layer, and an n-typesemiconductor layer stacked in the upper direction from the bottom.

A first insulating layer 281 is disposed on a lower surface of the firstepitaxial stack 220, in particular, a surface of the first epitaxialstack 220 facing the substrate 200. A plurality of contact holes areformed in the first insulating layer 281. The ohmic electrode 225 p′contacting the p-type semiconductor layer of the first epitaxial stack220 is provided in the contact hole. The ohmic electrode 225 p′ may beformed of various materials. In an exemplary embodiment, the ohmicelectrode 225 p′ corresponding to a p-type ohmic electrode may includeAu(Zn) or Au(Be). In this case, since the reflectance of a materialforming the ohmic electrode 225 p′ may be lower than that of a materialsuch as Ag, Al, or Au, an additional reflection electrode may be furtherdisposed. For example, Ag, Au, etc. may be used as a material for theadditional reflection electrode, and a metallic adhesive layer formed ofa material such as Ti, Ni, Cr, or Ta may be disposed for adhesion withan adjacent component. In this case, the metallic adhesive layer may bethinly deposited on an upper surface and a lower surface of a reflectionelectrode including Ag, Au, etc.

The first p-type contact electrode 225 p (e.g., the data line 2120)contacts the ohmic electrode 225 p′. The first p-type contact electrode225 p is provided between the first insulating layer 281 and the firstadhesive layer 260 a.

The first p-type contact electrode 225 p may overlap the first epitaxialstack 220, in particular, a light emitting region of the first epitaxialstack 220 in a plan view, and may be provided to cover all or most ofthe light emitting region. The first p-type contact electrode 225 p mayinclude a reflective material to reflect light emitted from the firstepitaxial stack 220. The first insulating layer 281 may also include areflective material to reflect light emitted from the first epitaxialstack 220. For example, the first insulating layer 281 may have anomni-directional reflector (ODR) structure.

The first wavelength pass filter 271 and the first n-type contactelectrode 221 n are provided on an upper surface of the first epitaxialstack 220.

The first wavelength pass filter 271 is provided on the upper surface ofthe first epitaxial stack 220 to cover substantially all the lightemitting region of the first epitaxial stack 220.

The first n-type contact electrode 221 n may be provided in a regioncorresponding to the first contact part 220 c and may be formed of aconductive material. A contact hole is provided in the first wavelengthpass filter 271, and the first n-type contact electrode 221 n contactsthe n-type semiconductor layer of the first epitaxial stack 220 throughthe contact hole.

The second adhesive layer 260 b is provided on the second epitaxialstack 230, and the second n-type contact electrode 231 n and the secondepitaxial stack 230 are sequentially provided on the second adhesivelayer 260 b. The second epitaxial stack 230 may include an n-typesemiconductor layer, an active layer, and a p-type semiconductor layerstacked in the upper direction from the bottom.

In an exemplary embodiment, the area of the second epitaxial stack 230may be smaller than the area of the first epitaxial stack 220. A regionof the second epitaxial stack 230 that corresponds to the first contactpart 220 c is removed, and thus, a portion of an upper surface of thefirst n-type contact electrode 221 n is exposed. Also, the area of thesecond epitaxial stack 230 may be smaller than the area of the secondn-type contact electrode 231 n. A region of the second epitaxial stack230 that corresponds to the second contact part 230 c is removed, andthus, a portion of an upper surface of the second n-type contactelectrode 231 n is exposed.

The second p-type contact electrode 235 p, the second wavelength passfilter 273, and the third p-type contact electrode 245 p aresequentially provided on an upper surface of the second epitaxial stack230. The area of the second wavelength pass filter 273 may be similar tothe area of the second epitaxial stack 230, and the second wavelengthpass filter 273 may have a contact hole in a partial region thereof. Thesecond p-type contact electrode 235 p and the third p-type contactelectrode 245 p may be physically and electrically connected to eachother through the contact hole. The contact hole may be formed inplural, and may be provided in a region corresponding to a particularcontact part, for example, the third contact part 240 c. Alternatively,a portion where the second p-type contact electrode 235 p and the thirdp-type contact electrode 245 p are connected to each other may bevaried.

The third epitaxial stack 240 is provided on the third p-type contactelectrode 245 p. The second epitaxial stack 230 may include a p-typesemiconductor layer, an active layer, and an n-type semiconductor layerstacked in the upper direction from the bottom.

The area of the third epitaxial stack 240 may be smaller than the areaof the second epitaxial stack 230. The area of the third epitaxial stack240 may be smaller than the area of the third p-type contact electrode245 p, and thus, a portion of an upper surface of the third p-typecontact electrode 245 p may be exposed.

A second insulating layer 283 covering a stacked structure of the first,second, and third epitaxial stacks 220, 230, and 240 is disposed on thethird epitaxial stack 240. The second insulating layer 283 may be formedof various organic/inorganic insulation materials, such as an inorganicinsulation material including silicon nitride, silicon oxide, etc. ororganic insulation materials including polyimide, without being limitedthereto.

The first contact hole CH1 exposing the upper surface of the firstn-type contact electrode 221 n may be formed in the second insulatinglayer 283. The first scan line 2130R is connected to the first n-typecontact electrode 221 n through the first contact hole CH1.

A third insulating layer 285 is provided on the second insulating layer283. The third insulating layer 285 may include substantially the samematerial as the second insulating layer 283. The third insulating layer285 may also be formed of various organic/inorganic insulationmaterials, but the inventive concepts are not limited to a particularmaterial of the second and third insulating layers 283 and 285.

The second and third scan lines 2130G and 2130B and the bridge line 2120b are provided on the third insulating layer 285.

The second contact hole CH2 exposing an upper surface of the secondn-type contact electrode 231 n at the second contact part 230 c, thethird contact hole CH3 exposing an upper surface of the third epitaxialstack 240, e.g., the n-type semiconductor layer of the third epitaxialstack 240 at the third contact part 240 c, and the fourth and fifthcontact holes CH4 and CH5 exposing an upper surface of the third p-typecontact electrode 245 p and an upper surface of the first p-type contactelectrode 225 p at the common contact part 250 c are provided in thethird insulating layer 285.

The second scan line 2130G is connected to the second n-type contactelectrode 231 n through the second contact hole CH2. The third scan line2130B is connected to the n-type semiconductor layer of the thirdepitaxial stack 240 through the third contact hole CH3.

The data line 2120 is connected with the third p-type contact electrode245 p through the bridge line 2120 b provided on the fourth contact holeCH4 and the fifth contact hole CH5. Since the third p-type contactelectrode 245 p is connected with the second p-type contact electrode235 p and forms a shared electrode, and the first p-type contactelectrode 225 p corresponds to the data line 2120, each of the first,second, and third p-type contact electrodes 225 p, 235 p, and 245 p isconnected through the bridge line 2120 b.

The third scan line 2130B may directly contact the n-type semiconductorlayer of the third epitaxial stack 240 and may be electrically connectedthereto. However, the inventive concepts are not limited thereto, and insome exemplary embodiments, a third n-type contact electrode may befurther provided between the third scan line 2130B and the n-typesemiconductor layer of the third epitaxial stack 240.

In an exemplary embodiment, a concavo-convex portion may be selectivelyprovided on an upper surface of each of the first, second, and thirdepitaxial stacks 220, 230, and 240. The concavo-convex portion may beprovided only in a portion corresponding to a light emitting region ofeach semiconductor layer, or may be provided over the entire uppersurface of each semiconductor layer.

In an exemplary embodiment, a light non-transmissive layer may befurther provided on a side surface of the third insulating layer 285,which corresponds to a side surface of a pixel. The lightnon-transmissive layer may be a light blocking layer including a lightabsorbing or reflecting material to prevent light from the first,second, and third epitaxial stacks 220, 230, and 240 from being outputtoward a side of the light emitting stacked structure.

The light non-transmissive layer is not specifically limited as long asit absorbs or reflects light. In an exemplary embodiment, the lightnon-transmissive layer may be a DBR dielectric mirror or a metallicreflection layer formed on an insulating layer, or may be an organicpolymer layer of a black color. When the metallic reflection layer isused as the light non-transmissive layer, the metallic reflection layermay be electrically insulated from an element of pixels.

When the light non-transmissive layer is provided on a side surface ofthe pixel, light from a particular pixel may be prevented frominfluencing an adjacent pixel or cause a color mixing phenomenon withlight emitted from an adjacent pixel.

A pixel described above may be fabricated by sequentially stacking thefirst, second, and third epitaxial stacks 220, 230, and 240 on thesubstrate 200, which will be described in more detail below.

FIGS. 47, 49, 51, 53, 55, and 57 are plan views illustrating a method ofsequentially stacking first, second, and third epitaxial stacks on asubstrate according to an exemplary embodiment.

FIGS. 48, 50A to 50C, 52A to 52H, 54A to 54D, 56, and 58 arecross-sectional views taken along line I-I′ of FIGS. 47, 49, 51, 53, 55,and 57.

Referring to FIGS. 47 and 48, the first epitaxial stack 220 and theohmic electrode 225 p′ are formed on a first temporary substrate 210 p.

The first temporary substrate 210 p may be a semiconductor substrate forforming the first epitaxial stack 220, and may be, for example, a GaAssubstrate. The first epitaxial stack 220 is formed by stacking an n-typesemiconductor layer, an active layer, and a p-type semiconductor layeron the first temporary substrate 210 p.

The first insulating layer 281 is formed on the first temporarysubstrate 210 p, and the ohmic electrode 225 p′ is formed in a contacthole of the first insulating layer 281.

The ohmic electrode 225 p′ may be formed by forming the first insulatinglayer 281 on the first temporary substrate 210 p, coating a photoresist,patterning the photoresist, depositing a material for the ohmicelectrode 225 p′ on the patterned photoresist, and lifting off thephotoresist pattern. However, the inventive concepts are not limitedthereto. For example, the ohmic electrode 225 p′ may be formed byforming the first insulating layer 281, patterning the first insulatinglayer 281 through photolithography, forming an ohmic electrode layer byusing a material for the ohmic electrode 225 p′, and patterning theohmic electrode layer through photolithography.

Referring to FIGS. 49 and 50A, a first p-type contact electrode 225 p(e.g., data line 2120) is formed on the first temporary substrate 210 pon which the ohmic electrode 225 p′ is formed. The first p-type contactelectrode 225 p may be formed of a reflective material. The first p-typecontact electrode 225 p may be formed, for example, by depositing ametallic material and patterning the deposited material by usingphotolithography.

Referring to FIGS. 49 and 50B, the first epitaxial stack 220 formed onthe first temporary substrate 201p may be inverted and attached on thesubstrate 200 on which the first adhesive layer 260 a is formed.

Referring to FIGS. 49 and 50C, the first temporary substrate 210 p isremoved after the first epitaxial stack 220 is attached on the substrate200. The first temporary substrate 210 p may be removed by variousmethods such as wet etching, dry etching, physical removal, and laserlift-off.

In some exemplary embodiments, a concavo-convex portion may be formed onan upper surface (or on an n-type semiconductor layer) of the firstepitaxial stack 220, after the first temporary substrate 210 p isremoved,. The concavo-convex portion may be formed through texturingusing various etching processes. For example, the concavo-convex portionmay be formed through various methods, such as dry etching using a microphoto process, wet etching using a crystalline property, texturing usinga physical method such as sandblast, ion beam etching, and texturingusing an etching speed difference of block copolymer.

Referring to FIGS. 51 and 52A, the first n-type contact electrode 221 nand the first wavelength pass filter 271 are formed on an upper surfaceof the first epitaxial stack 220.

The first n-type contact electrode 221 n may be formed by forming thefirst wavelength pass filter 271 on the first epitaxial stack 220,coating a photoresist, patterning the photoresist, depositing a materialfor the first n-type contact electrode 221 n on the patternedphotoresist, and lifting off the photoresist pattern. However, theinventive concepts are not limited thereto, and may be formed throughphotolithography using two sheets of masks, for example.

Referring to FIGS. 51 and 52B, the third epitaxial stack 240, the thirdp-type contact electrode 245 p, and the second wavelength pass filter273 are formed on a second temporary substrate 210 q.

The second temporary substrate 210 q may include a sapphire substrate.The third epitaxial stack 240 is formed by stacking an n-typesemiconductor layer, an active layer, and a p-type semiconductor layeron the second temporary substrate 210 q.

The second wavelength pass filter 273 may be formed to be smaller thanthe third epitaxial stack 240 and the third p-type contact electrode 245p, or may be formed to have a contact electrode therein. The secondwavelength pass filter 273 may be patterned through photolithography.

Referring to FIGS. 51 and 52C, the second p-type contact electrode 235 pis formed on the second temporary substrate 210 q on which the secondwavelength pass filter 273 is formed. The second p-type contactelectrode 235 p may be formed to have a thickness enough to cover a stepthat may be caused when the second wavelength pass filter 273 is notformed. Since the second p-type contact electrode 235 p directlycontacts the third p-type contact electrode 245 p, the third p-typecontact electrode 245 p and the second p-type contact electrode 235 pare integrally formed in a region where the second wavelength passfilter 273 is not provided.

After the second p-type contact electrode 235 p is formed, aplanarization process may be performed on an upper surface of the secondp-type contact electrode 235 p. When forming the second p-type contactelectrode 235 p, a void may be formed at a step, which may be formedwhen the second wavelength pass filter 273 is not formed, but lightscattering due to the void may not be significant.

Referring to FIGS. 51 and 52D, the second epitaxial stack 230 and thesecond p-type contact electrode 235 p are formed on a third temporarysubstrate 201 r, and the second epitaxial stack 230 may be inverted andattached on the second temporary substrate 210 q on which the secondp-type contact electrode 235 p is formed.

The third temporary substrate 210 r may include a sapphire substrate.The third epitaxial stack 240 is formed by stacking an n-typesemiconductor layer, an active layer, and a p-type semiconductor layeron the third temporary substrate 210 r.

In an exemplary embodiment, the second p-type contact electrode 235 pmay be formed in both sides of the second temporary substrate 200 q andthe third temporary substrate 200 r facing each other with substantiallythe same material, to improve bonding between the two substrates.

Referring to FIGS. 51 and 52E, the third temporary substrate 210 r isremoved after the second epitaxial stack 230 is attached on the thirdepitaxial stack 240. The third temporary substrate 210 r may be removedby various methods, such as wet etching, dry etching, physical removal,and laser lift-off. For example, when the third temporary substrate 210r is a sapphire substrate, the sapphire substrate may be removed by alaser lift-off method, a stress lift-off method, a mechanical lift-offmethod, a physical polishing method, etc.

Referring to FIGS. 51 and 52F, the second n-type contact electrode 231 nis formed on the second epitaxial stack 230 of the second temporarysubstrate 210 q, on which the second and third epitaxial stacks 230 and240 are formed.

Referring to FIGS. 51 and 52G, the second temporary substrate 210 q, onwhich the second and third epitaxial stacks 230 and 240 are formed, isinverted and attached on the first epitaxial stack 220 with the secondadhesive layer 260 b interposed therebetween. In this case, the secondn-type contact electrode 231 n and the first wavelength pass filter 271are disposed to face each other.

Referring to FIGS. 51 and 52H, the second temporary substrate 210 q isremoved after the second and third epitaxial stacks 230 and 240 areattached on the first epitaxial stack 220. The second temporarysubstrate 201q may be removed by various methods, such as wet etching,dry etching, physical removal, and laser lift-off. For example, when thesecond temporary substrate 210 q is a sapphire substrate, the sapphiresubstrate may be removed by a laser lift-off method, a stress lift-offmethod, a mechanical lift-off method, a physical polishing method, etc.

As such, the first, second, and third epitaxial stacks 220, 230, and 240are stacked on the substrate 200. According to an exemplary embodiment,after the second temporary substrate 210 q is removed, a concavo-convexportion may be formed on an upper surface (or on an n-type semiconductorlayer) of the third epitaxial stack 240. The concavo-convex portion maybe formed through texturing using various etching processes. Theconcavo-convex portion may be formed by using a patterned sapphiresubstrate with concavo-convex as the second temporary substrate. In thiscase, the concavo-convex portion on the third epitaxial stack 240 may beeasily formed. When the patterned sapphire substrate is removed from thethird epitaxial stack 240, the concavo-convex portion on the patternedsapphire substrate may be transferred to the third epitaxial stack 240.

Referring to FIGS. 53 and 54A, the first p-type contact electrode 225 pof the first epitaxial stack 220 is connected to the data line 2120.However, since the first n-type contact electrode 221 n of the firstepitaxial stack 220 is not connected to the first scan line 2130R, andis also not connected with the second and third scan lines 2130G and2130B of the second and third epitaxial stacks 230 and 240 and the dataline 2120, a process for a connection with the first, second, and thirdscan lines 2130R, 2130G, and 2130B and the data line 2120 is performedin a later process.

In particular, the third epitaxial stack 240 is patterned. Substantialportions of the third epitaxial stack 240 are removed except for thelight emitting region. In particular, portions of the third epitaxialstack 240 corresponding to the first and second contact parts 220 c and230 c and the common contact part 250 c are removed. The third epitaxialstack 240 may be removed by various methods, such as wet etching or dryetching using photolithography. In this case, the third p-type contactelectrode 245 p may function as an etch stopper.

Referring to FIGS. 53 and 54B, the third p-type contact electrode 245 p,the second wavelength pass filter 273, the second p-type contactelectrode 235 p, and the second epitaxial stack 230 are removed in aregion except for the light emitting region. In particular, portions ofthe third p-type contact electrode 245 p that correspond to the firstcontact part 220 c and the second contact part 230 c, the secondwavelength pass filter 273, the second p-type contact electrode 235 p,and the second epitaxial stack 230 are removed. The third p-type contactelectrode 245 p, the second wavelength pass filter 273, the secondp-type contact electrode 235 p, and the second epitaxial stack 230 maybe removed by various methods, such as wet etching or dry etching usingphotolithography. In this case, the second n-type contact electrode 231n may function as an etch stopper.

Referring to FIGS. 53 and 54C, the second n-type contact electrode 231 nand the second adhesive layer 260 b are removed in a region except forthe light emitting region. In particular, portions of the second n-typecontact electrode 231 n and the second adhesive layer 260 b thatcorrespond to the first contact part 220 c are removed. As such, anupper surface of the first n-type contact electrode 221 n on the firstcontact part 220 c is exposed. The second n-type contact electrode 231 nand the second adhesive layer 260 b may be removed by various methods,such as wet etching or dry etching using photolithography.

Referring to FIGS. 53 and 54D, the first wavelength pass filter 271, thefirst epitaxial stack 220, and the first insulating layer 281 areremoved in a region except for the light emitting region to expose anupper surface of the first p-type contact electrode 225 p. The firstwavelength pass filter 271, the first epitaxial stack 220, and the firstinsulating layer 281 may be removed by various methods, such as wetetching or dry etching using photolithography. In this case, the firstp-type contact electrode 225 p may function as an etch stopper.

Referring to FIGS. 55 and 56, the second insulating layer 283 having aplurality of contact holes is formed on the first, second, and thirdepitaxial stacks 220, 230, and 240 that are patterned, and the firstscan line 2130R is formed on the second insulating layer 283. The secondinsulating layer 283 has the first contact hole CH1 in a regioncorresponding to the first contact part 220 c, and an upper surface ofthe first n-type contact electrode 221 n is exposed by the first contacthole CH1. The first scan line 2130R is connected to the first n-typecontact electrode 221 n through the first contact hole CH1. In someexemplary embodiments, in addition to the first contact hole CH1, dummycontact holes CH' may be selectively formed in the second insulatinglayer 283. The dummy contact holes CH' may be provided in regionscorresponding to the second contact part 230 c, the third contact part240 c, and the common contact part 250 c. The dummy contact holes CH'may decrease the slope of inner side walls of second to fourth contactholes formed in the second contact part 230 c, the third contact part240 c, and the common contact part 250 c to be formed later.

The second insulating layer 283 and the first scan line 2130R may beformed by various methods, for example, through photolithography usingplural sheets of masks. In an exemplary embodiment, the secondinsulating layer 283 having the first contact hole CH1 and the dummycontact holes CH′ may be formed by forming the insulating layer 283 onsubstantially the entire surface of the substrate 200, and patterningthe insulating layer 283 by using photolithography. Next, the first scanline 2130R may be formed by coating a photoresist on the substrate 200on which the second insulating layer 283 is formed, patterning thephotoresist, depositing a material for the first scan line 2130R on thepatterned photoresist, and lifting off the photoresist pattern.

Referring to FIGS. 57 and 58, the third insulating layer 285 is formedon the substrate 200 on which the first scan line 2130R is formed, andthe second scan line 2130G, the third scan line 2130B, and the bridgeline 2120 b are formed on the third insulating layer 285.

The second scan line 2130G, the third scan line 2130B, and the bridgeline 2120 b may be formed on the third insulating layer 285 by variousmethods, for example, through photolithography using plural sheets ofmasks.

In an exemplary embodiment, the third insulating layer 285 having thesecond, third, fourth, and fifth contact holes CH2, CH3, CH4, and CH5 isformed. Here, the second, third, and fourth contact holes CH2, CH3, andCH4 may be formed by removing the third insulating layer 285 in thedummy contact holes. More particularly, the second contact hole CH2 isformed in a region corresponding to the second contact part 230 c, thethird contact hole CH3 is formed in a region corresponding to the thirdcontact part 240 c, and the fourth contact hole CH4 is formed in aregion corresponding to the common contact part 250 c. The fifth contacthole CH5 is further formed in the region corresponding to the commoncontact part 250 c, together with the second, third, and fourth contactholes CH2, CH3, and CH4. As such, an upper surface of the second n-typecontact electrode 231 n is exposed by the second contact hole CH2, anupper surface of the third epitaxial stack 240 is exposed by the thirdcontact hole CH3, an upper surface of the third p-type contact electrode245 p is exposed by the fourth contact hole CH4, and an upper surface ofthe first p-type contact electrode 225 p is exposed by the fifth contacthole CH5.

Next, the second scan line 2130G, the third scan line 2130B, and thebridge line 2120 b are formed.

The second scan line 2130G, the third scan line 2130B, and the bridgeline 2120 b may be formed by coating a photoresist on the substrate 200on which the third insulating layer 285 is formed, patterning thephotoresist, depositing a material for the second scan line 2130G, thethird scan line 2130B, and the bridge line 2120 b on the patternedphotoresist, and lifting off the photoresist pattern. As such, thesecond scan line 2130G is connected to the second n-type contactelectrode 231 n through the second contact hole CH2, and the third scanline 2130B is connected to an n-type semiconductor layer of the thirdepitaxial stack 240 through the third contact hole CH3. The bridge line2120 b is connected to the third p-type contact electrode 245 p by thefourth contact hole CH4 and is connected to the first p-type contactelectrode 225 p by the fifth contact hole CH5.

In an exemplary embodiment, a light non-transmissive layer may befurther provided on a side surface of a pixel, in which a secondinsulating layer 283 and/or a third insulating layer 285 is formed. Thelight non-transmissive layer may be implemented as a DBR dielectricmirror, a metallic reflection layer formed on an insulating layer, or anorganic polymer layer. When the metallic reflection layer is used as thelight non-transmissive layer, the light non-transmissive layer may beformed to be in a floating state with other elements of the pixel forelectrical insulation. In an exemplary embodiment, the lightnon-transmissive layer may be formed by depositing two insulating layersof different refractive indices. For example, the light non-transmissivelayer may be formed by sequentially stacking a material of a lowrefractive index and a material of a high refractive index, or bystacking insulating layers of different refractive indices, such as SiO₂and SiN_(x).

As described above, according to the exemplary embodiments, it ispossible to simultaneously form a wire part and contacts at a pluralityof epitaxial stacks after sequentially stacking the plurality ofepitaxial stacks.

According to an exemplary embodiment, a light emitting stacked structureincludes a shared electrode between second and third epitaxial stacks,and p-type and n-type contact electrodes are respectively provided on anupper surface and a lower surface a first epitaxial stack without a mesastructure. However, the inventive concepts are not limited thereto, andthe shared electrode may be provided between the second and thirdepitaxial stacks, and the first epitaxial stack may have a mesastructure, in which both the p-type contact electrode and the n-typecontact electrode are provided on a lower surface thereof.

FIG. 59A is a schematic plan view of a display apparatus according to anexemplary embodiment, and FIG. 59B is a cross-sectional view taken alongline A-B of FIG. 59A.

Referring to FIGS. 59A and 59B, the display apparatus according to anexemplary embodiment may include a substrate 351, electrode pads 353 a,353 b, 353 c, and 353 d, a first LED stack 323, a second LED stack 333,a third LED stack 343, a first reflective electrode 325, a first ohmicelectrode 325 n, first auxiliary electrodes 325 d, a ground layer 328,second auxiliary electrodes 328 d, a second transparent electrode 335, athird transparent electrode 345, a first color filter 337, a secondcolor filter 347, an underfill 355, a first bonding layer 365, and asecond bonding layer 375. The display apparatus may further include bumppads 330 a, 330 b, 330 c, and 330 d, a plurality of connectors 359 b,359 c, 359 d, 369 b, 369 c, 369 d, 379 c, and 379 d, and insulatinglayers 326, 327, 329, 357, 367, and 377.

The substrate 351 supports the LED stacks 323, 333, and 343. Inaddition, the substrate 351 may have circuits disposed therein. Forexample, the substrate 351 may be a silicon substrate in which thin filmtransistors (TFTs) are formed. A TFT substrate has been widely used foractive matrix driving in a display field, such as a liquid crystaldisplay (LCD) field, or the like. Since a structure of the TFT substrateis well known in the art, detailed descriptions thereof will be omitted.

Although FIGS. 59B shows a cross-sectional view of a unit pixel disposedon the substrate 351, a plurality of unit pixels may be arranged on thesubstrate 351, and may be driven by an active matrix method.

The electrode pads 353 a, 353 b, 353 c, and 353 d are disposed on thesubstrate 351. The electrode pads 353 a, 353 b, 353 c, and 353 dcorresponding to the respective unit pixels are disposed on thesubstrate 351. The electrode pads 353 a, 353 b, 353 c, and 353 d areeach connected to the circuits in the substrate 351. Although theelectrode pad 353 d is described as being provided to each unit pixel,in some exemplary embodiments, the electrode pad 353 d may not beprovided to all pixels. As will be described in more detail below, theground layer 328 is may be continuously disposed over the pixels.Therefore, the electrode pad 353 d may be provided to only one of thepixels.

The first LED stack 323, the second LED stack 333, and the third LEDstack 343 each includes an n-type semiconductor layer, a p-typesemiconductor layer, and an active layer interposed between the n-typesemiconductor layer and the p-type semiconductor layer. In particular,the active layer may have a multiple quantum well structure.

The first, second, and third LED stacks 323, 333, and 343 emit lighthaving a longer wavelength as being disposed closer to the substrate351. For example, the first LED stack 323 may be an inorganic lightemitting diode emitting red light, the second LED stack 333 may be aninorganic light emitting diode emitting green light, and the third LEDstack 343 may be an inorganic light emitting diode emitting blue light.The first LED stack 323 may include a GaInP based well layer, and thesecond LED stack 333 and the third LED stack 343 may include a GaInNbased well layer. However, the inventive concepts are not limitedthereto. When the pixel includes a micro LED, which has a surface arealess than about 10,000 square μm as known in the art, or less than about4,000 square μm or 2,500 square μm in other exemplary embodiments, thefirst LED stack 323 may emit any one of red, green, and blue light, andthe second and third LED stacks 333 and 343 may emit a different one ofred, green, and blue light, without adversely affecting operation, dueto the small form factor of a micro LED.

In addition, both surfaces of each LED stack 323, 333, or 343 are ann-type semiconductor layer and a p-type semiconductor layer,respectively. Hereinafter, an upper surface of each of the first,second, and third LED stacks 323, 333, and 343 will be described as ann-type and a lower surface of each of the first, second, and third LEDstacks 323, 333, and 343 will be described as a p-type. However, theinventive concepts are not limited thereto, and the type of thesemiconductor of the upper surface and the lower surface of each of theLED stacks may be reversed.

When the upper surface of the third LED stack 343 is an n-type, aroughened surface may be formed on the upper surface of the third LEDstack 343 by surface texturing through chemical etching. Roughenedsurfaces may also be formed on the upper surfaces of the first LED stack323 and the second LED stack 333 by surface texturing. In general, greenlight has higher visibility than red light or blue light. As such, whenthe second LED stack 333 emits green light, the surface texturing may beapplied to first LED stack 323 and the third LED stack, while no surfacetexturing or less surface texturing may be applied to the second LEDstack 333.

In this manner, light extraction efficiency may be improved in the firstLED stack 323 and the third LED stack to make luminous efficiencysubstantially uniform between the LED stacks.

The first LED stack 323 is disposed closer to the substrate 351, thesecond LED stack 333 is disposed on the first LED stack 323, and thethird LED stack 343 is disposed on the second LED stack. Since the firstLED stack 323 according to an exemplary embodiment may emit light havinga longer wavelength than that of the second and third LED stacks 333 and343, light generated in the first LED stack 323 may be emitted to theoutside through the second and third LED stacks 333 and 343. Inaddition, since the second LED stack 333 according to an exemplaryembodiment may emit light having a longer wavelength than that of thethird LED stack 343, light generated in the second LED stack 333 may beemitted to the outside through the third LED stack 343.

The first reflective electrode 325 is in ohmic contact with the p-typesemiconductor layer of the first LED stack 323, and reflects the lightgenerated in the first LED stack 323. For example, the first reflectiveelectrode 325 may include an ohmic contact layer 325 a and a reflectivelayer 325 b.

The ohmic contact layer 325 a is in partial contact with the p-typesemiconductor layer. The ohmic contact layer 325 a may be formed in alimited area to prevent absorption of light by the ohmic contact layer325 a. The ohmic contact layer 325 a may be in contact with the firstLED stack 323 in at least one region. The ohmic contact layer 325 a maybe formed of a transparent conductive oxide or an Au alloy, such as AuZnor AuBe.

The reflective layer 325 b covers the ohmic contact layer 325 a and thelower surface of the first LED stack 323. The reflective layer 325 b mayinclude a reflective metal layer, such as Al, Ag, or Au. In addition,the reflective layer 325 b may include an adhesive metal layer, such asTi, Ta, Ni, or Cr, on upper and lower surfaces of the reflective metallayer to improve adhesion of the reflective metal layer. The reflectivelayer 325 b may be formed of a metal layer having a high reflectance tolight generated in the first LED stack 323, for example, red light. Thereflective layer 325 b may have a low reflectance to light generated inthe second LED stack 333 and the third LED stack 343, for example, greenlight or blue light. As such, the reflective layer 325 b may absorblight generated in the second and third LED stacks 333 and 343 andtraveling toward the substrate 351 to decrease optical interference. Forexample, Au may be used as the material forming the reflective layer 325b in the first LED stack 323 because of its high reflectance to redlight and its low reflectance to blue light and green light.

In some exemplary embodiments, the ohmic contact layer 325 a may beomitted and the first reflective electrode 325 may include thereflective layer 325 b including an Au alloy, such as AuZn or AuBe,which has high reflectivity and capable of forming an ohmic contact.

The first reflective electrodes 325 are spaced apart from each other inregions where the connectors 359 b, 359 c, and 359 d are to be formed,and the first auxiliary electrodes 325 d formed of substantially thesame material as that of the reflective layer 325 b may be disposed inthese regions. The first auxiliary electrodes 325 d may be formed toprevent steps from being generated when the bump pads 330 a, 330 b, 330c, and 330 d are formed, but may be omitted in some exemplaryembodiments. The first auxiliary electrodes 325 d are spaced apart fromthe first LED stack 323 by the insulation layer 326.

The first ohmic electrode 325 n is disposed on the upper surface of thefirst LED stack 323, and is in ohmic contact with the n-typesemiconductor layer of the first LED stack 323. The first ohmicelectrode 325 n may be formed of an Au alloy, such as AuGe.

The insulation layer 326 may be disposed between the first reflectiveelectrode 325 and the first LED stack 323, and may have at least oneopenings 326 a (see FIG. 62B) exposing the lower surface of the LEDstack 323. The ohmic contact layer 325 may be disposed in the opening326 a, or the reflective layer 325 b may be in ohmic contact with thep-type semiconductor layer of the first LED stack 323 through theopening 326 a.

The insulation layer 327 may be disposed between the first reflectiveelectrode 325 and the first auxiliary electrodes 325 d, and thesubstrate 351, and may have openings exposing the first reflectiveelectrode 325 and the first auxiliary electrodes 325 d.

The ground layer 328 is disposed between the insulation layer 327 andthe substrate 351. The ground layer 328 may be connected to one of thefirst auxiliary electrodes 325 d through the opening of the insulationlayer 327. When the auxiliary electrodes 325 d are omitted, the groundlayer 328 may be in contact with the insulation layer 326 or may bespaced apart from the insulation layer 326 to be disposed on theinsulation layer 327. The ground layer 328 may be formed of a conductivematerial layer, for example, metal. The ground layer 328 may be disposedin only one pixel region or be continuously disposed in a plurality ofpixel regions.

The ground layer 328 is electrically insulated from the first reflectiveelectrode 325. The ground layer 328 is electrically connected in commonto the n-type semiconductor layers of the first, second, and third LEDstacks 323, 333, and 343. Therefore, the ground layer 328 is insulatedfrom the first reflective electrode 325, which is electrically connectedto the p-type semiconductor layer of the first LED stack 323.

The second auxiliary electrodes 328 d may be disposed in the openings ofthe insulation layer 327. The second auxiliary electrodes 328 d may beformed on the same plane as the ground layer 328 and may includesubstantially the same material as the ground layer 328. The secondauxiliary electrodes 328 d are disposed to prevent steps from beinggenerated when the bump pads 330 a, 330 b, 330 c, and 330 d are formed,but may be omitted in some exemplary embodiments. One of the secondauxiliary electrodes 328 d may be connected to the reflective electrode325, and the others of the second auxiliary electrodes 328 d may bedisposed on the first auxiliary electrodes 325 d, respectively.

The insulation layer 329 may be disposed between the ground layer 328and the second auxiliary electrodes 328 d, and the substrate 351, andmay have openings exposing the ground layer 328 and the second auxiliaryelectrodes 328 d.

The bump pads 330 a, 330 b, 330 c, and 330 d are disposed between theground layer 328 and the second auxiliary electrodes 328 d, and theelectrode pads 353 a, 353 b, 353 c, and 353 d to electrically connectthe ground layer 328 and the second auxiliary electrodes 328 d to theelectrode pads 353 a, 353 b, 353 c, and 353 d to each other. The bumppads 330 a, 330 b, 330 c, and 330 d may be formed on the ground layer328 and the second auxiliary electrodes 328 d through the openings ofthe insulation layer 329, and may be bonded to the electrode pads 353 a,353 b, 353 c, and 353 d. The bump pad 330 d may be provided to all ofthe pixels, but the inventive concepts are not limited thereto. Forexample, the bump pad 330 d may be selectively formed in the pixels, asthe electrode pad 353 d.

The underfill 355 fills spaces between the bump pads 330 a, 330 b, 330c, and 330 d and the electrode pads 353 a, 353 b, 353 c, and 353 d toprotect the bump pads 330 a, 330 b, 330 c, and 330 d and the electrodepads 353 a, 353 b, 353 c, and 353 d, and to reinforce adhesion of thebump pads 330 a, 330 b, 330 c, and 330 d. In some exemplary embodiments,an anisotropic conductive film (ACF) may be used instead of theunderfill 355. The ACF may be disposed between the bump pads 330 a, 330b, 330 c, and 330 d, and the electrode pads 353 a, 353 b, 353 c, and 353d to electrically connect the bump pads 330 a, 330 b, 330 c, and 330 dand the electrode pads 353 a, 353 b, 353 c, and 353 d to each other.

The second transparent electrode 335 may be in ohmic contact with thep-type semiconductor layer of the second LED stack 333. The secondtransparent electrode 335 may be formed of a metal layer or a conductiveoxide layer that is transparent to red light and green light. The thirdtransparent electrode 345 may be in ohmic contact with the p-typesemiconductor layer of the third LED stack 333. The third transparentelectrode 345 may be formed of a metal layer or a conductive oxide layerthat is transparent to red light, green light, and blue light. Thesecond transparent electrode 335 and the third transparent electrode 345may be in ohmic contact with the p-type semiconductor layer of each LEDstack to assist current distribution. For example, the conductive oxidelayer used for the second and third transparent electrodes 335 and 345may include SnO₂, InO₂, ITO, ZnO, IZO, or others.

The first color filter 337 may be disposed between the first LED stack323 and the second LED stack 333. The second color filter 347 may bedisposed between the second LED stack 333 and the third LED stack 343.The first color filter 337 transmit light generated in the first LEDstack 323, and reflects light generated in the second LED stack 333. Thesecond color filter 347 transmits light generated in the first andsecond LED stacks 323 and 333, and reflects light generated in the thirdLED stack 343. As such, light generated in the first LED stack 323 maybe emitted to the outside through the second LED stack 333 and the thirdLED stack 343, and light emitted from the second LED stack 333 may beemitted to the outside through the third LED stack 343. Furthermore,light generated in the second LED stack 333 may be prevented from beinglost by being incident on the first LED stack 323, or light generated inthe third LED stack 343 may be prevented from being lost by beingincident on the second LED stack 333.

In some exemplary embodiments, the first color filter 337 may reflectlight generated in the third LED stack 343.

The first and second color filters 337 and 347 may be, for example, alow pass filter that passes only a low frequency range, e.g., a longwavelength band, a band pass filter that passes only a predeterminedwavelength band, or a band stop filter that blocks only a predeterminedwavelength band. In particular, the first and second color filters 337and 347 may be formed by alternately stacking insulation layers havingrefractive indices different from each other, for example, may be formedby alternately stacking TiO₂ and SiO₂ insulation layers. In particular,the first and second color filters 337 and 347 may include a distributedBragg reflector (DBR). A stop band of the distributed Bragg reflectormay be controlled by adjusting thicknesses of TiO₂ and SiO₂. The lowpass filter and the band pass filter may also be formed by alternatelystacking insulation layers having refractive indices different from eachother.

The first bonding layer 365 couples the second LED stack 333 to thefirst LED stack 323. As illustrated in the drawing, the first bondinglayer 365 may be in contact with the first LED stack 323, and may be incontact with the first color filter 337. The first bonding layer 365 maytransmit light generated in the first LED stack 323.

The second bonding layer 375 couples the third LED stack 343 to thesecond LED stack 333. As illustrated in the drawing, the first bondinglayer 375 may be in contact with the second LED stack 333, and may be incontact with the second color filter 347. However, the inventiveconcepts are not limited thereto, and a transparent conductive layer maybe disposed on the second LED stack 333. The second bonding layer 375may transmits light generated in the first LED stack 323 and the secondLED stack 333.

The bonding layers 365 and 375 may be formed by forming transparentorganic layers or transparent inorganic layers on each of two targetsbonded to each other and bonding the targets to each other. Examples ofthe organic layer may include SUB, poly(methylmethacrylate) (PMMA),polyimide, parylene, benzocyclobutene (BCB), or others, and examples ofthe inorganic layer include Al₂O₃, SiO₂, SiN_(x), or others. The organiclayers may be bonded at a high vacuum and a high pressure, and theinorganic layers may be bonded under a high vacuum when the surfaceenergy is lowered by using plasma or the like, after flattening surfacesby, for example, a chemical mechanical polishing process. In addition,the first and second bonding layers 365 and 375 may be formed of, forexample, light-transmissive spin-on-glass.

Meanwhile, a 1-1-th connector 359 d is adopted in order to electricallyconnect the n-type semiconductor layer of the first LED stack 323 to theground layer 328. The 1-1-th connector 359 d may connect the first ohmicelectrode 325 n to the first auxiliary electrode 325 d to which theground layer 328 is connected.

The 1-1-th connector 359 d may penetrate through the first LED stack323, and is electrically insulated from the p-type semiconductor layerof the first LED stack 323 by the insulation layer 357. The insulationlayer 357 may at least partially cover the upper surface of the firstLED stack 323, and may cover the first ohmic electrode 325 n. However,the insulation layer 357 may have openings exposing the first auxiliaryelectrodes 325 d and openings exposing the first ohmic electrode 325 n.The 1-1-th connector 359 d may be connected to the first auxiliaryelectrode 325 d and the first ohmic contact 325 n through the openingsof the insulation layer 357.

Although the 1-1-th connector 359 d is described as penetrating throughthe first LED stack 323, in some exemplary embodiments, the 1-1-thconnector 359 d may be formed on a side surface of the first LED stack323.

Meanwhile, a 1-2-th connector 359 b and a 1-3-th connector 359 c maypenetrate through the first LED stack 323 and be connected to the firstauxiliary electrodes 325 d. The 1-2-th connector 359 b and the 1-3-thconnector 359 c are insulated from the first LED stack 323. As such, theinsulation layer 357 may be interposed between the first LED stack 323and the 1-2-th connector 359 b and the 1-3-th connector 359 c.

Meanwhile, a 2-1-th connector 369 d is disposed to electrically connectthe n-type semiconductor layer of the second LED stack 333 to theelectrode pad 353 d. The 2-1-th connector 369 d may be connected to theupper surface of the second LED stack 333, and penetrate through thesecond LED stack 333. However, the inventive concepts are not limitedthereto, and the 2-1-th connector 369 d may be formed on a side surfaceof the second LED stack 333. Meanwhile, as illustrated in the drawing,the 2-1-th connector 369 d may be connected to the 1-1-th connector 359d to be electrically connected to the electrode pad 353 d. In addition,the 2-1-th connector 369 d may be stacked on the 1-1-th connector 359 din a vertical direction.

The insulation layer 367 may be interposed between the second LED stack333 and the 2-1-th connector 369 d in order to prevent the 2-1-thconnector 369 d from being short-circuited to the p-type semiconductorlayer of the second LED stack 333 and the second transparent electrode335. The insulation layer 367 may cover the upper surface of the secondLED stack 333, but may have openings in order to allow connection of the2-1-th connector 369 d.

A 2-2-th connector 369 b is disposed to electrically connect the secondtransparent electrode 335 to the electrode pad 353 b. The 2-2-thconnector 369 b is electrically connected to the p-type semiconductorlayer of the second LED stack 333 through the second transparentelectrode 335. As illustrated in the drawing, the 2-2-th connector 369 bmay penetrate through the second LED stack 333. However, the inventiveconcepts are not limited thereto, and the 2-2-th connector 369 b may beformed on a side surface of the second LED stack 333. The insulationlayer 367 is interposed between the 2-2-th connector 369 b and thesecond LED stack 333 to prevent the 2-2-th connector 369 b from beingshort-circuited to the upper surface of the second LED stack 333.

Additionally, a 2-3-th connector 369 c may be disposed to penetratethrough the second LED stack 333. The 2-3-th connector 369 c may beelectrically connected to the electrode pad 353 c, and may be connectedto, for example, the 1-3-th connector 359 c. The 2-3-th connector 369 cis insulated from the second LED stack 333. As such, the insulationlayer 367 may be interposed between the second LED stack 333 and the2-3-th connector 369 c.

The 2-3-th connector 369 c may function as an intermediate connector,and may be omitted in some exemplary embodiments.

Meanwhile, a 3-1-th connector 379 d is disposed to electrically connectthe upper surface of the third LED stack 343 to the electrode pad 353 d.The 3-1-th connector 379 d may be connected to the upper surface, thatis, the n-type semiconductor layer of the third LED stack 343, andpenetrate through the third LED stack 343. As illustrated in thedrawing, the 3-1-th connector 379 d may be connected to the 2-1-thconnector 369 d to be electrically connected to the electrode pad 353 d.

Meanwhile, the insulation layer 377 may be interposed between the thirdLED stack 343 and the 3-1-th connector 379 d in order to prevent the3-1-th connector 379 d from being short-circuited to the lower surfaceof the third LED stack 343. The insulation layer 377 may cover the uppersurface of the third LED stack 343, but may have openings exposing theupper surface of the third LED stack 343 in order to allow connection ofthe 3-1-th connector 379 d.

A 3-2-th connector 379 c is disposed to electrically connect the thirdtransparent electrode 345 to the electrode pad 353 c. The 3-2-thconnector 379 c is electrically connected to the lower surface of thethird LED stack 343 through the third transparent electrode 345. Asillustrated in the drawing, the 3-2-th connector 379 c may penetratethrough the third LED stack 343. However, the inventive concepts are notlimited thereto, and the 3-2-th connector 379 c may be formed on a sidesurface of the third LED stack 343. The insulation layer 377 isinterposed between the 3-2-th connector 379 c and the third LED stack343 to prevent the 3-2-th connector 379 c from being short-circuited tothe upper surface of the third LED stack 343.

As illustrated in the drawing, the 3-2-th connector 379 c may beconnected to the 2-3-th connector 369 c to be electrically connected tothe electrode pad 353 c. In this case, the 2-3-th connector 369 c andthe 1-3-th connector 359 c may function as intermediate connectors. Inaddition, as illustrated in the drawing, the 3-2-th connector 379 c maybe stacked on the 2-3-th connector 369 c in the vertical direction. Assuch, the 1-3-th connector 359 c, the 2-3-th connector 369 c, and the3-2-th connector 379 c are electrically connected to each other, and arestacked in the vertical direction. The 1-1-th connector 359 d, the2-1-th connector 369 d, and the 3-1-th connector 379 d may also bestacked in the vertical direction.

The connectors may be disposed along a path of light and absorb light.When the connectors are disposed to be spaced apart from each other in atransversal direction, an area through which light is emitted may bedecreased to increase light loss. According to an exemplary embodiment,since the connectors are stacked in the vertical direction, loss oflight generated in the first LED stack 323 and the second LED stack 333by the connectors may be suppressed.

In some exemplary embodiments, a light reflecting layer or a lightblocking material layer covering side surfaces of the first, second, andthird LED stacks 323, 333, and 343 may be formed to prevent opticalinterference between the pixels, which may occur when light is emittedthrough side surfaces of the first LED stack 323, the second LED stack333, and the third LED stack 343. For example, the light reflectinglayer may include a distributed Bragg reflector (DBR) or an insulationlayer formed of SiO₂ or the like, with a reflective metal layer or ahighly reflective organic layer deposited thereon. As another example, ablack epoxy may be used as the light blocking layer. In this manner, alight blocking material may prevent optical interference between lightemitting devices to increase a contrast of an image.

According to the illustrated exemplary embodiment, the first LED stack323 is electrically connected to the electrode pads 353 d and 353 a, thesecond LED stack 333 is electrically connected to the electrode pads 353d and 353 b, and the third LED stack 343 is electrically connected tothe electrode pads 353 d and 353 c. As such, cathodes of the first LEDstack 323, the second LED stack 333, and the third LED stack 343 areelectrically connected in common to the electrode pad 353 d, and anodesof the first LED stack 323, the second LED stack 333, and the third LEDstack 343 are electrically connected to different electrode pads 353 a,353 b, and 353 c, respectively. In this manner, the first, second, andthird LED stacks 323, 333, and 343 may be independently drivable.Furthermore, the first, second, and third LED stacks 323, 333, and 343are disposed on a thin film transistor substrate 351 and areelectrically connected to circuits in the substrate 351, so as to bedriven in an active matrix manner.

FIG. 60 is a schematic circuit diagram of a display apparatus accordingto an exemplary embodiment.

Referring to FIG. 60, a driving circuit according to an exemplaryembodiment includes two or more transistors Tr1 and Tr2 and capacitors.When a power supply is connected to selection lines Vrow1 to Vrow3 anddata voltages are applied to data lines Vdata1 to Vdata3, voltages areapplied to corresponding light emitting diodes. In addition, electriccharges are charged in corresponding capacitors depending on values ofVdata1 to Vdata3. Since a turn-on state of Tr2 may be maintained by acharging voltage of the capacitor, a voltage of the capacitor may bemaintained even though power supplied to Vrow1 is blocked, and a voltagemay be applied to light emitting diodes LED1 to LED3. In addition,currents flowing to LED1 to LED3 may be changed depending on the valuesof Vdata1 to Vdata3. The current may continuously supplied through Vdd,and continuous light emission is thus possible.

The transistors Tr1 and Tr2 and the capacitors may be formed in thecapacitor 351. LED1 to LED3 may correspond to the first, second, andthird stacks 323, 333, and 343 stacked in one pixel. Anodes of thefirst, second, and third LED stacks are connected to the transistor Tr2,and cathodes of the first, second, and third LED stacks are grounded. Inthe illustrated exemplary embodiment, the first, second, and third LEDstacks 323, 333, and 343 may be connected in common to the ground layer328 to be grounded. Further, the ground layer 328 may be continuouslydisposed in two or more pixels, and furthermore, in all of the pixels,and may be connected in common to all LED stacks in the displayapparatus. The ground layer 328 may be disposed between the pixels andthe substrate to remove noise of an active matrix driving circuit.

Although FIG. 61A shows a circuit diagram for driving a displayapparatus in active matrix manner, the inventive concepts are notlimited thereto, and various other circuits may also be used.

FIGS. 61A, 61B, 62A, 62B, 63A, 63B, 64A, 64B, 65A, 65B, 66A, 66B, 67A,67B, 68A, 68B, 69A, 69B, 70A, 70B, 71A, 71B, 72A, 72B, 73A, 73B, 74A,74B, 75A, and 75B are schematic plan views and cross-sectional viewsillustrating a method of manufacturing a display apparatus according toan exemplary embodiment of the present disclosure. In the drawings, eachplan view corresponds to a plan view of FIG. 59A, and eachcross-sectional view corresponds to a cross-sectional view taken alongline A-B of a corresponding plan view.

Referring to FIGS. 61A and 61B, the first LED stack 323 is grown on afirst substrate 321. The first substrate 321 may be, for example, a GaAssubstrate. The first LED stack 323 may be formed of AlGaInP basedsemiconductor layers, and includes an n-type semiconductor layer, anactive layer, and a p-type semiconductor layer.

The insulation layer 326 having openings 326 a is formed on the firstLED stack 323, and the ohmic contact layer 325 a and the reflectivelayer 325 b are formed, such that the first reflective electrode 325 isformed. The first reflective electrode 325 is formed in each pixelregion, and is electrically connected to the p-type semiconductor layerof the first LED stack 323. The ohmic contact layer 325 a may be formedin the openings of the insulation layer 326 by a lift-off technology orthe like.

The reflective layer 325 b is formed on the insulation layer 326, andcovers the ohmic contact layer 325 a. The reflective layer 325 b may beformed in regions except for three corner portions in each pixel region.The reflective layer 325 b may be formed by a lift-off technology or thelike. When the reflective layer 325 b includes an ohmic contactmaterial, the ohmic contact layer 325 a may be omitted in some exemplaryembodiments.

The first auxiliary electrodes 325 d are formed together with thereflective layer 325 b on the insulation layer 326. The first auxiliaryelectrodes 325 d may be formed together with the reflective layer 325 busing substantially the same material as that of the reflective layer325 b by the lift-off technology or the like. The first auxiliaryelectrodes 325 d may be disposed in the vicinity of three corners ofeach pixel region.

Referring to FIGS. 62A and 62B, the insulation layer 327 is formed onthe reflective layer 325 b and the first auxiliary electrodes 325 d. Theinsulation layer 327 has openings exposing the reflective layer 325 band the first auxiliary electrodes 325 d. The openings of the insulationlayer 327 may have substantially a rectangular shape as illustrated inthe drawings. However, the shape of the openings of the insulation layer327 is not limited thereto, and may have another shape in some exemplaryembodiments.

Referring to FIGS. 63A and 63B, the ground layer 328 and the secondauxiliary electrodes 328 d are formed on the insulation layer 327. Theground layer 328 may cover most of the pixel region, and may beconnected to one of the first auxiliary electrodes 325 d. One of thesecond auxiliary electrodes 328 d may be connected to the firstreflective electrode 325, and the remaining second auxiliary electrodes328 d may be disposed on the first auxiliary electrodes 325 d,respectively. In some exemplary embodiments, the first auxiliaryelectrodes 325 d and the second auxiliary electrodes 328 d may beomitted.

The ground layer 328 may be formed in each pixel region. However, theinventive concepts are not limited thereto, and the ground layer 328 maybe continuously formed in a plurality of pixel regions.

Referring to FIGS. 64A and 64B, the insulation layer 329 may be formedon the ground layer 328 and the second auxiliary electrodes 328 d. Theinsulation layer 329 has openings exposing the ground layer 328 and thesecond auxiliary electrodes 328 d.

The insulation layers 326, 327, and 328 described above may be formed ofan electrically insulating material, for example, a silicon oxide or asilicon nitride.

Then, the bump pads 330 a, 330 b, 330 c, and 330 d are formed. The bumppads 330 a, 330 b, 330 c, and 330 d are disposed on the ground layer 328and the second auxiliary electrode 328 d, respectively, through theopenings of the insulation layer 329. The bump pads 330 a, 330 b, and330 c, and the bump pad 330 d may be formed in each pixel region.However, the inventive concepts are not limited thereto, and the bumppad 330 d may be formed in some pixel regions or in only one pixelregion.

Referring to FIG. 65A, the second LED stack 333 is grown on a secondsubstrate 331, and the second transparent electrode 335 and the firstcolor filter 337 are formed on the second LED stack 333. The second LEDstack 333 may be formed of gallium nitride based semiconductor layers,and includes a GaInN well layer. The second substrate 331 is a substrateon which a gallium nitride based semiconductor layer may be grown, andmay be different from the first substrate 321. A composition ratio ofGaInN may be determined so that the second LED stack 333 may emit greenlight, for example. Meanwhile, the second transparent electrode 335 isin ohmic contact with the p-type semiconductor layer.

In addition, referring to FIG. 65B, the third LED stack 343 is grown ona third substrate 341, and the third transparent electrode 345 and thesecond color filter 347 are formed on the third LED stack 343. The thirdLED stack 343 may be formed of gallium nitride based semiconductorlayers, and includes a GaInN well layer. The third substrate 341 is asubstrate on which a gallium nitride based semiconductor layer may begrown, and may be different from the first substrate 321. A compositionratio of GaInN may be determined so that the third LED stack 343 mayemit blue light, for example. Meanwhile, the third transparent electrode345 is in ohmic contact with the p-type semiconductor layer.

The first color filter 337 and the second color filter 347 aresubstantially the same as those described with reference to FIGS. 59Aand 59B, and thus, detailed descriptions thereof will be omitted inorder to avoid redundancy.

Referring to FIGS. 66A and 66B, the electrode pads 353 a, 353 b, 353 c,and 353 d are formed on the substrate 351. The substrate 351 may be anSi substrate in which thin film transistors are formed. The electrodepads 353 a, 353 b, 353 c, and 353 d may be distributed and disposed infour corner regions so as to correspond one pixel region. The electrodepad 353 d may be formed in each pixel region. However, in some exemplaryembodiments, the electrode pad 353 d may be formed in only some pixelregions or be formed in only one pixel region.

The first LED stack 323, the second LED stack 333, the third LED stack343, and the electrode pads 353 a, 353 b, 353 c, and 353 d are formed ondifferent substrates, respectively, the order of forming the first LEDstack 323, the second LED stack 333, the third LED stack 343, and theelectrode pads 353 a, 353 b, 353 c, and 353 d is not particularlylimited.

Referring to FIGS. 67A and 67B, the bump pads 330 a, 330 b, 330 c, and330 d are bonded onto the substrate 351, such that the first LED stack323 is coupled to the substrate 351. The underfill 355 may fill a spacebetween the substrate 351 and the first LED stack 323. In some exemplaryembodiments, an anisotropic conductive film (ACF) may be disposedbetween the bump pads 330 a, 330 b, 330 c, and 330 d and the substrate351, instead of the underfill 355.

The first substrate 321 is removed from the first LED stack 323 by achemical etching technology or the like. As such, the n-typesemiconductor layer of the first LED stack 323 is exposed to the uppersurface. A roughened surface may be formed on a surface of the exposedn-type semiconductor layer by surface texturing in order to improvelight extraction efficiency.

Referring to FIGS. 68A and 68B, the first ohmic electrode 325 n may beformed on the exposed first LED stack 323. The first ohmic electrode 325n may be formed in each pixel region.

Then, the first LED stack 323 is patterned, such that openings exposingthe first auxiliary electrodes 325 d are formed. When the first LEDstack 323 is patterned, the first LED stacks 323 may be separated fromeach other for each pixel region.

Referring to FIGS. 69A and 69B, the insulation layer 357 is formed tocover side surfaces of the first LED stack 323 in the openings. Theinsulation layer 357 may also at least partially cover the upper surfaceof the first LED stack 323. The insulation layer 357 is formed to exposethe first auxiliary electrodes 325 d and the first ohmic electrode 325n.

Then, the connectors 359 b, 359 c, and 359 d each connected to theexposed first auxiliary electrodes 325 d are formed. The 1-1-thconnector 359 d is connected to the first ohmic electrode 325 n, and tothe first auxiliary electrode 325 d to which the ground layer 328 isconnected. As such, the n-type semiconductor layer of the first LEDstack 323 is electrically connected to the ground layer 328.

The 1-2-th connector 359 b and the 1-3-th connector 359 c are insulatedfrom the first LED stack 323 by the insulation layer 357. The 1-2-thconnector 359 b is electrically connected to the electrode pad 353 b,and the 1-3-th connector 359 c is electrically connected to theelectrode pad 353 c.

Referring to FIGS. 70A and 70B, the second LED stack 333 of FIG. 65A iscoupled onto the first LED stack 323, in which the 1-1-th, 1-2-th, and1-3-th connectors 359 d, 359 b, and 359 c are formed, through the firstbonding layer 365. The first color filter 337 is disposed to face thefirst LED stack 323 and is bonded to the first bonding layer 365. Thefirst bonding layer 365 may be disposed in advance on the first LEDstack 323, and the first color filter 337 may be disposed to face thefirst bonding layer 365 and be bonded to the first bonding layer 365.Alternatively, bonding material layers are formed on the first LED stack323 and the first color filter 337, respectively, and are bonded to eachother, such that the second LED stack 333 may be coupled to the firstLED stack 323. Meanwhile, the second substrate 331 may be separated fromthe second LED stack 333 by a technique, such as a laser lift-off, achemical lift-off, or others. As such, the n-type semiconductor layer ofthe second LED stack 333 is exposed. The exposed n-type semiconductorlayer may be surface-textured by chemical etching or the like. However,in some exemplary embodiments, surface texturing for the second LEDstack 333 may be omitted.

Referring to FIGS. 71A and 71B, the second LED stack 333 is patterned,such that the second transparent electrode 335 is exposed, the exposedsecond transparent electrode 335 is partially etched, and the firstcolor filter 337 and the first bonding layer 365 are then etched, suchthat an opening exposing the 1-1-th connector 359 d is formed. Inaddition, openings exposing the 1-2-th connector 359 b and the 1-3-thconnector 359 c may be formed together by penetrating through the secondLED stack 333, the second transparent electrode 335, the first colorfilter 337, and the first bonding layer 365. Furthermore, the second LEDstacks 333 may be separated from each other for each pixel region.

Referring to FIGS. 72A and 72B, the insulation layer 367 covering sidesurfaces of the exposed openings is formed. The insulation layer 367 mayalso cover the upper surface of the second LED stack 333. However, theinsulation layer 367 exposes the second transparent electrode 335, andalso exposes the 1-1-th connector 359 d, the 1-2-th connector 359 b, andthe 1-3-th connector 359 c. In addition, the insulation layer 367partially exposes the upper surface of the second LED stack 333.

Then, the 2-1-th connector 369 d, the 2-2-th connector 369 b, and the2-3-th connector 369 c are formed in the openings. The 2-1-th connector369 d electrically connects the exposed upper surface of the second LEDstack 333 to the 1-1-th connector 359 d. As such, the n-typesemiconductor layer of the second LED stack 333 is electricallyconnected to the ground layer 328. The 2-1-th connector 369 d isinsulated from the p-type semiconductor layer of the second LED stack333 and the second transparent electrode layer 35 by the insulationlayer 367.

The 2-2-th connector 369 b electrically connects the second transparentelectrode 335 and the 1-2-th connector 359 b to each other, and isinsulated from the upper surface of the second LED stack 333 by theinsulation layer 367. The second transparent electrode 335 iselectrically connected to the electrode pad 353 b through the 2-2-thconnector 369 b, the 1-2-th connector 359 b, the bump pad 330 b, and thelike. As such, the p-type semiconductor layer of the second LED stack333 is electrically connected to the electrode pad 353 b, and the n-typesemiconductor layer of the second LED stack 333 is electricallyconnected to the electrode pad 353 d.

The 2-3-th connector 369 is connected to the 1-3-th connector 359 c, andis insulated from the second LED stack 333 and the second transparentelectrode 335 by the insulation layer 367.

Referring to FIGS. 73A and 73B, the third LED stack 343 of FIG. 65B iscoupled onto the second LED stack 333, in which the 2-1-th, 2-2-th, and2-3-th connectors 369 d, 369 b, and 369 c are formed, through the secondbonding layer 375. The second color filter 347 may be disposed to facethe second LED stack 333 and be bonded to the second bonding layer 375.The second bonding layer 375 may be disposed in advance on the secondLED stack 333, and the second color filter 347 may be disposed to facethe second bonding layer 375 and be bonded to the second bonding layer375. Alternatively, bonding material layers are formed on the second LEDstack 333 and the second color filter 347, respectively, and are bondedto each other, such that the third LED stack 343 may be bonded to thesecond LED stack 333. Meanwhile, the third substrate 341 may beseparated from the third LED stack 343 by a technique such as a laserlift-off, a chemical lift-off, or others. As such, the n-typesemiconductor layer of the third LED stack 343 is exposed. The exposedn-type semiconductor layer may be surface-textured by chemical etchingor the like.

Referring to FIGS. 74A and 74B, the third LED stack 343 is patterned,such that the third transparent electrode 345 is exposed, the exposedthird transparent electrode 345 is partially etched, and the secondcolor filter 347 and the second bonding layer 375 are etched, such thatan opening exposing the 2-1-th connector 369 d is formed. In addition,an opening exposing the 2-3-th connector 369 c is formed by penetratingthrough the third LED stack 343, the third transparent electrode 345,the second color filter 347, and the second bonding layer 375.

Referring to FIGS. 75A and 75B, the insulation layer 377 covering sidesurfaces of the exposed openings is formed. However, the insulationlayer 377 exposes the third transparent electrode 345, and also exposesthe 2-1-th connector 369 d and the 2-3-th connector 369 c. Furthermore,the insulation layer 377 may cover the upper surface of the LED stack343, but partially expose the upper surface of the LED stack 343.

Then, the 3-1-th connector 379 d and the 3-2-th connector 379 c areformed in the openings. The 3-1-th connector 379 d connects the uppersurface, e.g., the n-type semiconductor layer of the third LED stack 343to the 2-1-th connector 369 d. As such, the n-type semiconductor layerof the third LED stack 343 is electrically connected to the ground layer328.

The 3-2-th connector 379 b electrically connects the third transparentelectrode 345 and the 2-3-th connector 369 c to each other, and isinsulated from the upper surface of the third LED stack 343 by theinsulation layer 377. The third transparent electrode 345 iselectrically connected to the electrode pad 353 c through the 3-2-thconnector 379 c, the 2-3-th connector 369 c, the 1-3-th connector 359 c,the bump pad 330 c, and the like.

According to the illustrated exemplary embodiment, the cathodes of thefirst, second, and third LED stacks 323, 333, and 343 are electricallyconnected in common to the ground layer 328 and the electrode pad 353 d,and the anodes of the first, second, and third LED stacks 323, 333, and343 are independently connected to the electrode pads 353 a, 353 b, and353 c, respectively, is provided in a pixel.

Although FIGS. 61A to 75B show a method of manufacturing one unit pixelaccording to an exemplary embodiment, a plurality of unit pixels may bearranged in a matrix form on the substrate 351, and a display unit maybe formed in substantially similar manner. The first, second, and thirdLED stacks 323, 333, and 343 are disposed to be separated from eachother on the substrates 321, 331, and 341 so as to correspond the unitpixels. However, the ground layer 328 may be continuously disposed in aplurality of pixel regions. In this manner, since a plurality of pixelsare formed at a wafer level, pixels having a small size may not need tobe individually mounted.

Furthermore, a light reflecting layer or a light blocking material layercovering side surfaces of the pixels may be additionally formed toprevent optical interference between the pixels. For example, the lightreflecting layer may include a distributed Bragg reflector (DBR) or aninsulation layer formed of SiO₂, or the like, with a reflective metallayer or a highly reflective organic layer deposited thereon. Forexample, a black epoxy may be used as the light blocking layer, whichmay prevent optical interference between light emitting devices andincrease a contrast of an image.

FIGS. 76A and 76B are, respectively, a schematic plan view andcross-sectional view of a display apparatus according to anotherexemplary embodiment.

Referring to FIGS. 76A and 76B, the display apparatus according to anexemplary embodiment is different from the display apparatus describedabove in that the reflective layer 325 b, the first auxiliary electrodes325 d, and the insulation layer 327 are omitted, and the ground layer328 and the second auxiliary electrodes 328 d are formed on the ohmiccontact layer 325 a and the insulation layer 326.

The ground layer 328 and the second auxiliary electrodes 328 d may beformed of substantially the same material as that of the reflectivelayer 325 b. As such, the ground layer 328 and the second auxiliaryelectrodes 328 d may serve as the reflective layer 325 b. To this end,the ohmic contact layer 325 may be formed in only a region below one ofthe auxiliary electrodes 328 d.

The insulation layer 329 and the bump pads 330 a, 330 b, 330 c, and 330d are formed on the ground layer 328 and the second auxiliary electrodes328 d as described with reference to FIGS. 64A and 64B, and thesubsequent processes may be performed in substantially the same mannerdescribed above. However, since the reflective layer 325 b and the firstauxiliary electrodes 325 d are omitted, the 1-1-th connector 359 d isdirectly connected to the ground layer 328, and the 1-2-th connector 359b and the 1-3-th connector 359 c are connected to the second auxiliaryelectrodes 328 d, respectively.

FIGS. 77A and 77B are, respectively, a schematic plan view andcross-sectional view of a display apparatus according to anotherexemplary embodiment.

Referring to FIGS. 77A and 77B, the display apparatus according to anexemplary embodiment is substantially the same as the display apparatusof FIGS. 76A and 76B in that the reflective layer 325 b and the firstauxiliary electrodes 325 d are omitted. However, the display apparatusaccording to the illustrated exemplary embodiment is different in thatohmic contact layers 25 a are disposed in a plurality of regions, and ashape of one of second auxiliary electrodes 328 d is changed such thatone of the second auxiliary electrodes 328 d electrically connects theohmic contact layers 25 a to each other.

FIG. 78 is a schematic cross-sectional view of a display apparatusaccording to yet still another exemplary embodiment.

Referring to FIG. 78, the display apparatus according to an exemplaryembodiment is substantially similar to the display apparatus describedwith reference to FIGS. 59A and 59B, except that it further includes alight guide layer 381 disposed above the third LED stack 343.

The light guide layer 381 may cover the third LED stack 343 and theinsulation layer 377. The light guide layer 381 may guide light emittedthrough a surface of the third LED stack 343 to prevent opticalinterference between the pixels. The light guide layer 381 may include amaterial layer having a refractive index different from that of thethird LED stack 343 and the insulation layer 377.

FIG. 79 is a schematic cross-sectional view illustrating a displayapparatus according to yet still another exemplary embodiment.

Referring to FIG. 79, the display apparatus according to an exemplaryembodiment is substantially similar to the display apparatus describedwith reference to FIG. 78 except that the light guide layer 391 includesa light guide hole 391h to guide light. The light guide layer 391 may beformed of a light reflecting material or a light absorbing material. Assuch, the light guide layer 391 may reflect or absorb and block lighttraveling toward an adjacent pixel region to prevent opticalinterference between the pixels. Examples of the light reflectingmaterial may include a light reflecting material such as a white photosensitive solder resistor (PSR), and examples of the light absorbingmaterial may include a black epoxy, or others. In addition, a roughenedsurface R is formed on the upper surface of the third LED stack 343.

FIGS. 80A, 80B, 80C, and 80D are schematic cross-sectional views of adisplay apparatus according to exemplary embodiments.

Referring to FIG. 80A, the display apparatus according to an exemplaryembodiment is substantially similar to the display apparatus describedwith reference to FIG. 79 except that the hole 391h of the light guidelayer 391 are filled with a transparent material 393. The transparentmaterial 393 has a refractive index different from that of the lightguide layer 391. As such, internal total reflection may occur on aninterface between the transparent material 393 and the light guide layer391, such that light emitted to the outside may be guided.

The hole is formed in the light guide layer 391, the light guide layer391 is covered with the transparent material 393, and the transparentmaterial 393 is flattened by chemical mechanical polishing until thelight guide layer 391 is exposed, such that the hole of the light guidelayer 391 may be filled with the transparent material 393.

An upper surface of the transparent material 393 may be parallel to anupper surface of the light guide layer 391, but may have a convexsurface that protrudes upwardly compared to the upper surface of thelight guide layer 391 as shown in FIG. 80B, or may have a concavesurface that is depressed downwardly compared to the upper surface ofthe light guide layer 391 as shown in FIG. 80C. When the upper surfaceof the transparent material 393 has a convex surface, light may beconcentrated to improve illuminance, and when the upper surface of thetransparent material 393 has a concave surface, a direction angle oflight may be increased. A shape of the upper surface of the transparentmaterial 393 may be adjusted through a polishing speed of a chemicalmechanical polishing process, for example.

In addition, although inner walls of the hole of the light guide layer391 are described as being inclined, in some exemplary embodiments, theinner walls of the hole of the light guide layer 391 may be variousmodified, such as being vertically formed, as illustrated in FIG. 80D.

FIG. 81 is a schematic cross-sectional view of a display apparatusaccording to yet still another exemplary embodiment.

Referring to FIG. 81, the display apparatus according to an exemplaryembodiment is substantially similar to the display apparatus describedwith reference to FIGS. 80A, 80B, 80C, and 80D except that it furtherincludes a micro lens 395.

An upper surface the micro lens 395 may have a convex lens shape, butthe inventive concepts are not limited thereto. The micro lens 395 isdisposed on each pixel region, and narrows a viewing angle of emittedlight to prevent optical interference between the pixels.

The micro lens 395 may be formed by a photolithograph process, and maybe formed of, for example, polyimide, silicone, or others. A width ofthe micro lens 395 may be about 200 micrometers or less, morespecifically, 100 micrometers or less.

Although certain exemplary embodiments and implementations have beendescribed herein, other embodiments and modifications will be apparentfrom this description. Accordingly, the inventive concepts are notlimited to such embodiments, but rather to the broader scope of theappended claims and various obvious modifications and equivalentarrangements as would be apparent to a person of ordinary skill in theart.

What is claimed is:
 1. A light emitting stacked structure comprising: aplurality of epitaxial sub-units disposed one over another, eachepitaxial sub-unit configured to emit colored light having a differentwavelength band from each other; and a common electrode disposed betweenand connected to adjacent epitaxial sub-units, wherein light emittingregions of the epitaxial sub-units overlap each other.
 2. The lightemitting stacked structure claim 1, wherein the epitaxial sub-unitscomprise a first epitaxial stack, a second epitaxial stack, and a thirdepitaxial stack sequentially disposed one over another.
 3. The lightemitting stacked structure claim 2, wherein the common electrodecomprises a shared electrode disposed between one of i) the firstepitaxial stack and the second epitaxial stack, and ii) the secondepitaxial stack and the third epitaxial stack.
 4. The light emittingstacked structure claim 3, further comprising: a contact part disposedon the epitaxial sub-units to apply a common voltage and light emittingsignals, the contact part comprising: a common contact part to apply thecommon voltage to the first, second, and third epitaxial stacks; and afirst contact part, a second contact part, and a third contact part toapply the light emitting signals to the first, second, and thirdepitaxial stacks, respectively.
 5. The light emitting stacked structureclaim 4, further comprising: a first signal line, a second signal line,and a third signal line to apply the light emitting signals to thefirst, second, and third epitaxial stacks, respectively; and a commonline applying the common voltage to the first, second, and thirdepitaxial stacks, wherein the first, second, and third signal lines areconnected to the first, second, and third contact parts, respectively,and the common line is connected to the common contact part.
 6. Thelight emitting stacked structure claim 5, wherein the first, second, andthird signal lines extend in a first direction and the common lineextends in a second direction intersecting the first direction.
 7. Thelight emitting stacked structure claim 4, wherein: the common contactpart comprises a first common contact electrode, a second common contactelectrode, and a third common contact electrode to apply the commonvoltage to the first, second, and third epitaxial stacks, respectively;and the second and third common contact electrodes comprise the sharedelectrode.
 8. The light emitting stacked structure claim 7, wherein eachof the first, second, and third epitaxial stacks comprises a p-typesemiconductor layer, an active layer, and an n-type semiconductor layer.9. The light emitting stacked structure claim 8, wherein a stackedsequence of the n-type semiconductor layer, the active layer, and thep-type semiconductor layer in the second epitaxial stack is differentfrom that in at least one of the first and third epitaxial stacks. 10.The light emitting stacked structure claim 9, wherein the sharedelectrode directly contacts the p-type semiconductor layer of the secondepitaxial stack and the p-type semiconductor layer of the thirdepitaxial stack.
 11. The light emitting stacked structure claim 8,wherein: in the second epitaxial stack, the p-type semiconductor layer,the active layer, and the n-type semiconductor layer are stackedsequentially, and in the third epitaxial stack, the n-type semiconductorlayer, the active layer, and the p-type semiconductor layer are stackedsequentially.
 12. The light emitting stacked structure claim 1, whereinthe shared electrode directly contacts the n-type semiconductor layer ofthe second epitaxial stack and the n-type semiconductor layer of thethird epitaxial stack.
 13. The light emitting stacked structure claim 7,further comprising a wavelength pass filter disposed between the secondcommon contact electrode and the third common contact electrode.
 14. Thelight emitting stacked structure claim 13, wherein the second and thirdcommon contact electrodes are connected to each other through a contacthole provided in the wavelength pass filter.
 15. The light emittingstacked structure claim 7, wherein the first common contact electrode isdisposed under the first epitaxial stack.
 16. The light emitting stackedstructure claim 15, further comprising an insulating layer covering thefirst, second, and third epitaxial stacks, wherein the first commoncontact electrode is connected to the second and third common contactelectrodes through a contact hole formed in the insulating layer. 17.The light emitting stacked structure claim 1, wherein energy bands oflight emitted from the epitaxial sub-units increase from a lowermostepitaxial sub-unit to an uppermost epitaxial sub-unit.
 18. The lightemitting stacked structure claim 1, wherein the epitaxial sub-units areindependently drivable.
 19. The light emitting stacked structure claim1, wherein light emitted from a lower epitaxial sub-unit is configuredto transmit through an upper epitaxial sub-unit.
 20. The light emittingstacked structure claim 19, wherein each of the epitaxial sub-units isconfigured to transmit at least about 80% of light emitted from a lowerepitaxial sub-unit.
 21. The light emitting stacked structure claim 1,wherein the epitaxial sub-units comprise: a first epitaxial stackdisposed on a substrate and configured to emit a first color light; asecond epitaxial stack disposed on the first epitaxial stack andconfigured to emit a second color light having a wavelength banddifferent from the first color light; and a third epitaxial stackdisposed on the second epitaxial stack and configured to emit a thirdcolor light having a wavelength band different from the first and secondcolor light.
 22. The light emitting stacked structure claim 21, whereinthe first color light, the second color light, and the third color lightare red light, green light, and blue light, respectively.
 23. The lightemitting stacked structure claim 22, further comprising a firstwavelength pass filter disposed between the first epitaxial stack andthe second epitaxial stack.
 24. The light emitting stacked structureclaim 23, further comprising a second wavelength pass filter disposedbetween the second epitaxial stack and the third epitaxial stack. 25.The light emitting stacked structure claim 22, wherein at least one ofthe first to third epitaxial stacks has a concave-convex pattern formedon one upper surface thereof.
 26. A display device comprising: aplurality of pixels, at least one of the pixels comprises a lightemitting stacked structure comprising: a plurality of epitaxialsub-units disposed one over another, each epitaxial sub-unit configuredto emit colored light having a different wavelength band from eachother; and a common electrode disposed between and connected to adjacentepitaxial sub-units, wherein light emitting regions of the epitaxialsub-units overlap each other.
 27. The display device of claim 26,wherein the display device is driven in a passive matrix manner.
 28. Thedisplay device of claim 26, wherein the display device is driven in anactive matrix manner.